Effect of Translational Energy on the Chemisorption ofN2on Fe(111): Activated Dissociation via a Precursor State

The initial dissociative chemisorption probability of ${\mathrm{N}}_2$ on Fe(111) is found to increase by a factor of ≃${10}^5$ with increasing kinetic energy, rising from ≃1×${10}^{-6\mathrm{}}$ at ≃0.09 eV to over 1×${10}^{-1\mathrm{}}$ at 4.3 eV. This probability also increases with decreasing surface temperature, suggesting that reagent energy provides access to an intermediate state, such as $\alpha$-${\mathrm{N}}_2$, whose population also increases with kinetic energy, consistent with the accepted mechanism at low energies.