Orientation and desorption of oxygen admolecules on a Pt(113) stepped surface

摘要

The desorption and orientation of molecular oxygen on a Pt(113) or (s)2(111)x(100) stepped surface were studied by thermal desorption spectroscopy (TDS) and near edge X-ray absorption fine structure (NEXAFS). In TDS spectra, the direct desorption from admolecules yields three peaks, α_1-O_2 at 218 K, α_2-O_2 at 182 K, and α_3-O_2 at 162 K. The admolecules yielding α_1 and α_2-O_2 are adsorbed on step sites. α_1-O_2 is concluded to be parallel to step edges. On the other hand, α_3-O_2 declines from the bulk surface plane. It is suggested to be on terrace sites.