A remarkable heavy atom isotope effect in the dissociative chemisorption of nitrogen on Ru(001)

An extremely large isotope effect [I_eff=P_diss(¹⁵N₂)/P _diss(¹⁴N₂)], has been measured in the dissociative chemisorption of nitrogen molecules over Ru(001). It varies from unity at kinetic energies above 2 eV to 0.2 at E_k=1.4 eV. These observations are consistent with a barrier for direct dissociation of 1.8 eV, in agreement with previous experiments and recent ab initio density functional theory calculations. It supports earlier studies that proposed tunneling as the dissociation dynamics mechanism.