THE THERMAL CHEMISTRY OF ETHYL IODIDE CHEMISORBED ON NI(100)

The interaction of ethyl iodide with Ni(100) surfaces has been examined by using thermal programmed desorption (TPD), X-ray photoelectron (XPS), and static secondary ion mass (SSIMS) spectroscopies. Ethyl iodide adsorbs molecularly on that surface below 100 K, and dissociates between 100 and 160 K to form ethyl species and iodine atoms. At low coverages the ethyl moieties decompose completely to form surface carbon and hydrogen atoms (which recombine and desorb at slightly above 300 K), but desorption of both ethylene and ethane is also observed at higher coverages. Ethylene forms via the elimination of a hydrogen atom from the beta position, and desorbs between 160 and 210 K depending on the initial coverage of ethyl iodide; ethane, on the other hand, is generated mostly by a direct recombination of ethyl species with hydrogen originating either from adsorption of background gases or from the beta-hydride elimination reaction.