The mechanism of gas-surface reactions on metals can be far more complex than a net chemical equation would suggest. Many factors account for this complexity. The heterogeneity of the surface, and its ability to restructure can impact the availability and energetics of reaction sites. The distribution of energy among the vibrational, rotational, and translational degrees of freedom of the gas phase reactant, and the extent of surface excitation can all have a profound effect on transition state access and reaction probability, as can energy redistribution processes triggered by the gas-surface collision. <br/><br/>The talk will survey the ability of vibrational state selected measurements of gas-surface reactivity to systematically unravel important aspects of this complexity and provide molecular-level mechanistic insights that can guide our understanding and predictions about these processes. The experiments use infrared light to excite a single quantum rotational and vibrational level of the gas-surface reagent molecule and a molecular beam to define its incident kinetic energy. In this way, we are able to make energy-resolved measurements of reaction probability while systematically varying the distribution of energy among the system's energetic degrees of freedom. Computational studies by our collaborators inform and guide our interpretation of the data. <br/>Recent results will be featured and include assessing the impact of a vibrationally excited reagent molecule's symmetry on surface-induced energy redistribution, uncovering the role of surface atom motion on reaction energetics, and demonstrating how isolated surface structural features, including steps and adatoms, modify reaction energetics.

Shining light on complexity: State- and energy-resolved studies of gas-surface reaction dynamics and mechanism

2019 Spring National Meeting

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