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

High incident translational energy adsorption of oxygen on the reconstructe d Pt(100)-hex-R0.7 degrees surface was investigated with molecular beams, t hermal desorption spectroscopy and electron energy-loss spectroscopy. At 77 K and for kinetic energies as high as 1.1 eV, oxygen was observed to chemi sorb initially in two molecular states with intramolecular EELS loss featur es at 860 and 940 cm(-1). Thermal desorption spectra indicate only desorpti on 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 th e molecular state extending 0.13 eV above the energy of the approaching mol ecule. (C) 1999 Elsevier Science B.V. All rights reserved.