SYNTHESES AND REACTIONS OF VINYL AND PHENYL FRAGMENTS ON AG(111)

Low-energy electron activation of monolayer ethylene and benzene, adsorbed on Ag(111) at 100 K, leads selectively to vinyl and phenyl fragments. An electron impact ionization model, followed by rapid reneutralization and C-H bond cleavage, is proposed. Upon heating, neither fragment undergoes further C-H or C-C bond cleavage; rather, both undergo carbon-carbon coupling to form 1,3-butadiene and biphenyl. When coadsorbed with methyl or ethyl fragments, temperature-programmed desorption yields propene or 1-butene for vinyl, whereas it yields toluene or ethylbenzene for phenyl. Kinetic parameters describing the electron-stimulated fragment synthesis and the subsequent thermal reactions were determined in the presence and absence of atomic iodine.