H. Hamadeh et al., ADSORPTION OF ETHYLENE-OXIDE ON NI(110) - STRUCTURE, THERMAL AND RADIATION-INDUCED DECOMPOSITION, Surface science, 311(1-2), 1994, pp. 1-16
The adsorption and decomposition of ethylene oxide on Ni(110) at 95-35
0 K was investigated by LEED and mainly X-ray and UV photoelectron spe
ctroscopy. Thermal as well as photon-induced decomposition were discov
ered, with X-rays being about 10 times more efficient than UV photons
under the chosen experimental conditions. Photon-induced desorption of
ethylene oxide or of the decomposition products was negligible. The d
ecomposition itself was characterized by changes in valence band as we
ll as O 1s and C 1s core level spectra. A possible reaction pathway in
volves intermediates, such as methoxy, CH(x) and the final (at > 300 K
) species CO and carbon. A further possible intermediate, adsorbed ace
taldehyde, appears to be short-lived on Ni(110), as indicated by auxil
iary measurements with that species adsorbed at 95-150 K. The orientat
ion of ethylene oxide at 95-120 K is determined by angle-resolved core
level XPS intensity patterns, via the detection of O 1s or C 1s inten
sity enhancements. A tilted adsorption geometry is found, with the sym
metry axis of the molecule tilted towards the [001] or [001BAR] direct
ion by 48-degrees. The orientation is symmetric with respect to the [0
01] azimuth.