STRUCTURE OF BENZENE AND PHENOL CHEMISORBED ON NI(110)

The chemisorption of benzene and phenol on a clean Ni{110}-(1 x 1) surface and an oxygen predosed Ni{110}-(3 X 1)-O surface near room temperature has been investigated by time-of-flight scattering and recoiling spectrometry accompanied by shadow cone calculations. The Ne scattering and H, C, and O recoiling fluxes exhibited strong angular anisotropies as a function of beam incident (alpha) and crystal azimuthal (delta) angles. These anisotropies are due to C and O atoms shadowing their neighboring atoms within the benzene molecules and resulting phenoxide species, demonstrating that scattering and recoiling spectrometry is capable of providing structural information on polyatomic molecular systems. The results show that both benzene and phenoxide are chemisorbed as molecules which have very good short-range order despite the absence of long-range order observable by low energy electron diffraction. Both benzene and phenoxide are oriented nearly parallel to the surface, with a maximum inclination angle of 15-degrees. The C atoms in the para positions of benzene and the C-O bond in phenoxide are oriented along the [001] azimuth. The C-H bond is bent out of the plane of the hexagonal ring so that the H atoms are above the C atom plane. Chemisorption on the oxygen predosed surface results in a reaction in which a H atom is abstracted from both benzene and phenol with the formation of surface hydroxide groups; the molecules remain well ordered on this surface also.