DISSOCIATIVE CHEMISORPTION OF N-2 ON RU(001) ENHANCED BY VIBRATIONAL AND KINETIC-ENERGY - MOLECULAR-BEAM EXPERIMENTS AND QUANTUM-MECHANICALCALCULATIONS

The dissociation probability of N-2 on Ru(001) increases from 5 x 10(- 7) at a kinetic energy of 0.15 eV to 10(-2) at 4.0 eV. Vibrational exc itation of the impinging nitrogen molecules enhances the dissociation more than the equivalent energy in translation. Its relative importanc e increases as the incident kinetic energy grows. The dissociation was found to be surface temperature independent at all incident kinetic e nergies, in agreement with theoretical predictions based on quantum me chanical nonadiabatic calculations. These simulations reproduce accura tely the kinetic energy dependence of So over the entire energy range, suggesting that N-2 tunnels from the molecular to the adsorbed atomic state through an effective barrier of 2.2 eV.