SURFACE-CHEMISTRY OF METHYL NITRITE ON AG(111) - THERMAL AND NONTHERMAL PROCESSES

The thermal, electron and photon activation of methyl nitrite, CH3ONO, adsorbed on Ag(111) has been examined. Thermally there is no dissocia tion, and monolayers, which are weakly held, desorb at 131 K. Dissocia tion occurs readily when adsorbed CH3ONO is irradiated with either 50 eV electrons or photons with energies higher than 3.4 eV (lambda<365 n m). X-ray irradiation initiates dissociation and loss of N 1s and O 1s intensity that is consistent with ejection of NO. The only product ej ected during irradiation with ultraviolet photons is NO. The cross-sec tion for disappearance of the CH3ONO, as measured by its post-irradiat ion TPD peak area, is wavelength-dependent, generally rising with phot on energy between 3.4 eV and the highest energy used here, 4.9 eV (lam bda=254 mm). The cross-section is 0.26+/-0.04 x 10-18 cm(2) at 3.4 eV and 1.15+/-0.1 x 10(-18) cm(2) at 4.9 eV. For 50 eV electrons, NO is a lso dominant but is accompanied by small amounts of CH3, CH2O and CH3O H. The initial cross-section for loss of CH3ONO is 5+/-1x10(-16) cm(2) . Heating to 500 K after irradiation with electrons, X-rays or UV phot ons, leaves a clean Ag(111) surface. Among the products desorbed after photon or electron irradiation, methane and formaldehyde have been id entified.