Electron stimulated desorption of Ch 3OH and (CH 3) 2NH from partially oxidized copper

Abstract

Electron stimulated desorption (ESD) mass spectra of CH 3OH and (CH 3) 2NH adsorbed on partially oxidized polycrystalline copper exhibit mass fragments larger than H + for multilayer and submonolayer coverages, in contrast to previous photon stimulated desorption (PSD) studies of organic adsorbates on metal surfaces, for which only protons were observed at submonolayer coverages. For both molecules, the parent peak is absent from the mass spectrum of the adsorbed species even though present in the ESD spectrum of the gas phase. The (parent + H) ion is observed for both molecules at multilayer and submonolayer coverages, indicating the presence of the undissociated molecules at the surface, and also indicating that the absence of the parent ion from the ESD mass spectra of the adsorbed species is due to adsorbate-substrate interaction. These results demonstrate that ESD is a potential probe of both adsorbate structure and adsorbate-substrate interaction.