Dynamics of dissociative methane adsorption on metals: CH4 on Pt{110}(1x2)

Supersonic molecular beams have been used to study methane dissociative ads orption on Pt{110}(1 x 2) at incident translational energies of 20 to 700 m eV, incident vibrational temperatures of 300 to 800 K and surface temperatu res from 400 to 1000 K. At E(t)less than or equal to 100 meV, the initial d issociative sticking probability, s(0), rises sharply. The process is facil itated by vibrational excitation of the deformation modes and surface tempe rature. At E-t> 100 meV, an activated adsorption process becomes dominant, with an activation barrier of similar to 146 meV. At E(t)greater than or eq ual to 230 meV, s(0) attains a limiting value which is strongly enhanced by excitation of the C-H stretch modes in the incident molecule. An increase in the surface temperature also enhances s(0), at all incident translationa l energies. The mechanistic implications are discussed and it is concluded that the low translational energy process is a distinctive steering-assiste d direct adsorption pathway. (C) 2000 American Institute of Physics. [S0021 -9606(00)00510-9].