C-H bond activation on metals: A quantum dynamics model of direct and precursor mediated dissociation

We summarize here a recently developed quantum dynamical model to describe the dissociation of small alkanes on metal surfaces. This model is based on solving the dissociation dynamics quantum mechanically for a quasidiatomic R-H interacting with a metal surface through a reduced dimensionality potential energy surface. We find that for typical thermal conditions, both the direct (on-impact) dissociation and that due to precursor processes are dominated by tunneling, albeit in a somewhat more complicated form than usually envisioned in simple models. Because of this, we contend that traditional classical kinetic interpretations are not valid, e.g., an Arrhenius analysis of rates does not measure barrier parameters. © 1992, American Vacuum Society. All rights reserved.