Thermally assisted tunneling: ${\mathrm{CH}}_4$ dissociation on Pt(111)

The mechanism for the dissociation of ${\mathrm{CH}}_4$ at metal surfaces has been and is still controversial. In large part, this is because many of the experimental data suggest a direct tunneling mechanism, which is not obviously compatible with an observed strong dependence on the surface temperature. We propose here that a new phenomenon, thermally assisted tunneling, caused by a coupling of the tunnel barrier to the lattice, resolves this controversy. Explicit calculations using a simplified model for this process agree qualitatively with a wide range of experimental data for ${\mathrm{CH}}_4$ dissociation on Pt(111).