Evidence of a molecular chemisorption-mediated mechanism for high translational energy oxygen adsorption on Pt(100)-hex-R0.7°

High incident translational energy adsorption of oxygen on the reconstructed Pt(100)-hex-R0.7° surface was investigated with molecular beams, thermal desorption spectroscopy and electron energy-loss spectroscopy. At 77 K and for kinetic energies as high as 1.1 eV, oxygen was observed to chemisorb initially in two molecular states with intramolecular EELS loss features at 860 and 940 cm−1. Thermal desorption spectra indicate only desorption from these molecular states – no recombinative desorption was detected. Adsorption probability data over a range of surface temperatures support a model of direct molecular chemisorption with a dissociation barrier from the molecular state extending 0.13 eV above the energy of the approaching molecule.