INTERACTION OF HYDROGEN-ATOMS WITH COADSORBED D CH3I ADLAYERS ON NI(100) SURFACES - EVIDENCE FOR HOT ATOM MEDIATED REACTION/

Adlayers of coadsorbed hydrogen (deuterium) atoms and methyliodide, H/ CH3I, D/CH3I, H/CD3I, D/CD3I, were prepared on Ni(100) surfaces by ads orption of methyliodide on hydrogen (deuterium) saturated surfaces at 120 K. Upon directing thermal D (H) atoms at these adlayers as gaseous products hydrogen and methane molecules were observed which constitut e of surface species only, e.g., H-2 and CH4 in the combination: D-->H /CH3I. The rates of formation of these products give evidence for reac tion mechanisms in which adsorbed atoms, e.g., H, activated by collisi ons with incoming atoms, e.g., D, react with surface species, either H or CH3I to form H-2 and CH4. The reaction cross sections and isotope effects in H-->D/CD(H)(2)I or D-->H/CH(D)(3)I reactions support a coll ision:model in which:hot atoms act as mediators in the reaction pathwa ys. (C) 1997 American Institute of Physics.