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

An extremely large isotope effect [I-eff=P-diss(N-15(2))/P-diss(N-14(2))], has been measured in the dissociative chemisorption of nitrogen molecules o ver 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 dis sociation of 1.8 eV, in agreement with previous experiments and recent ab i nitio density functional theory calculations. It supports earlier studies t hat proposed tunneling as the dissociation dynamics mechanism. (C) 2000 Ame rican Institute of Physics. [S0021-9606(00)71119-6].