Site-specific fragmentation following C : 1s core-level photoionization of1,1,1-trifluoroethane condensed on a Au surface and of a 2,2,2-trifluoroethanol monolayer chemisorbed on a Si(100) surface

We used photoelectron spectroscopy, the energy-selected-photoelectron photo ion coincidence (ESPEPICO) method, the Auger electron photoion coincidence (AEPICO) method, and the ab initio method to study site-specific phenomena in the C:1s photoionization of 1,1,1-trifluoroethane (CF3CH3, TFEt) condens ed on a Au surface. Site-specific excitation and occurrence of different ch emical shifts at two carbon sites were evident in the total electron-yield spectrum and the photoelectron spectrum, and site-specific fragmentation wa s evident in the ESPEPICO spectrum. The fragmentation processes inferred fr om the ESPEPICO and AEPICO results were very different from those occurring in the vapor phase. We also studied the effect of the surface on the site- specific phenomena observed in a 2,2,2-trifluoroethanol (TFEtOH) monolayer chemisorbed on a Si(100) surface (CF3CH2OSi{substrate}). The molecular stru cture of TFEtOH is the same as that of TFEt except that it has a hydroxyl g roup substituted for one of the hydrogen atoms. Although site-specific phen omena were also observed in TFEtOH. the fragmentation process was very diff erent from that of TFEt because of the chemisorption structure of TFEtOH on Si(100).