Absolute dissociation cross sections for D2 dissociation on Pt steps

Abstract

Reaction mechanisms following gas-surface collisions may differ depending on the site of impact. On stepped Pt surfaces at least three dissociation mechanisms have been suggested to occur in parallel. Using supersonic molecular beams and a curved Pt single crystal, we unravel these site-dependent contributions and quantify absolute reaction cross sections using these mechanisms’ different dependencies on kinetic energy in the range of 0.7 to 13.4 kJ/mol. A sum of three dissociation mechanism probabilities fits our data well and allows us to extract absolute cross sections for indirect and direct non-activated dissociation at steps. We find good agreement with theoretical predictions.