The dissociative chemisorption dynamics of N₂ on catalytic metal surfaces: A quantum-mechanical tunneling mechanism

A tunneling mechanism is suggested for explaining the dissociative chemisorption of nitrogen molecules on metal surfaces. The time-dependent Schrödinger equation was numerically solved for the transition dynamics from the N₂-metal to the N-metal potential-energy surfaces for two degrees of freedom. The dynamics was found to be sensitive to the topology at the crossing region between the two nonadiabatic potential-energy surfaces (PES). The resulting rapid increase of the dissociation probability (S ₀) with incident kinetic energy, its saturation at high energies and vibrational enhancement are in good agreement with recent experiments. A substantial isotope effect is predicted by the calculations. Recombinative desorption experiments of ¹⁴N₂ and ¹⁵N ₂ from Re(0001) are in excellent agreement with the tunneling model.