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The state-resolved reactivity of CH₄ in its totally symmetric C-H stretch vibration (₁) has been measured on a Ni (100) surface. Methane molecules were accelerated to kinetic energies of 49 and 63. 5 kJ/mol in a molecular beam and vibrationally excited to ₁ by stimulated Raman pumping before surface impact at normal incidence. The reactivity of the symmetric-stretch excited CH₄ is about an order of magnitude higher than that of methane excited to the antisymmetric stretch (₃) reported by Juurlink et al. Phys. Rev. Lett. 83, 868 (1999) and is similar to that we have previously observed for the excitation of the first overtone (2₃). The difference between the state-resolved reactivity for ₁ and ₃ is consistent with predictions of a vibrationally adiabatic model of the methane reaction dynamics and indicates that statistical models cannot correctly describe the chemisorption of CH₄ on nickel.
Maroni et al. (Wed,) studied this question.