Paper SS-MoA4
State-Resolved Studies of Methane Activation: Mechanistic Insights into Gas-Surface Reactivity

Monday, October 29, 2012, 3:00 pm, Room 21

Gas-surface reactivity measurements performed with vibrational and rotational state selected reagents provide precise energetic resolution that can be exploited to uncover important aspects of gas-surface reactivity. This talk will focus on two examples. In the first, we explore the surface temperature dependent reactivity of methane (CH₄) molecules prepared in the ν₃ C-H stretching state. We find that at low incident kinetic energy, thermal excitation of the Ni(111) surface can increase reaction probability by nearly three orders of magnitude. Calculations from the Jackson group provide insight into the origin of this effect. As a second example, we will describe recent experiments that compare the reactivity of the symmetric (ν₁) and antisymmetric (ν₆) C-H stretching states in di-deutero methane, CH₂D₂, on Ni(111). That work explores how the vibrational symmetry of the reactant molecule may influence the rate and pathway of rapid intramolecular vibrational energy redistribution (IVR) that occurs just prior to reaction, and it tests whether vibrationally adiabatic models for methane activation in the gas phase are also applicable to methane reactivity on a metal surface.

Taken together, the work highlights how general patterns of energy flow within the gas-surface reaction complex can influence reactivity patterns, and how the kinetics of energy redistribution might be used to control or enhance the rate or selectivity of reactions on surfaces.