Dynamics of the formation of HD from D(H) atoms colliding with H(D) /Cu(111): A model study of an Eley-Rideal reaction

Abstract

It has long been postulated that gas-surface chemical reactions can occur upon a single gas-surface encounter, by an Eley-Rideal (ER) mechanism. In this paper, we describe results for the reaction of D(H) atoms with H(D)/Cu(111), which clearly confirmed that such direct gas-surface reactions indeed occur. We present angular and velocity distributions for the molecular products, as well as nascent internal-state distributions. We show that the angular distributions are asymmetric about the surface normal, providing proof of the direct nature of the reactions. We also show that the HD product has a very high degree of translational, vibrational, and rotational excitation, accounting for essentially all of the ∼ 2.3 eV available energy. Theses energies are in the order Ētrans > Évib > Érot. Strong isotope effects are observed, particularly in the angular and vibrational state distribution, where results for H-on-D are clearly different than those for D-on-H. We briefly compare our findings with the results of recent calculations.