| AVS 61st International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS+AS+EN-WeM |
| Session: | Dynamic Processes of Single Atoms and Molecules at Surfaces |
| Presenter: | Jason Navin, University of Virginia |
| Authors: | J.K. Navin, University of Virginia S.B. Donald, University of Virginia G. Cushing, University of Virginia I.A. Harrison, University of Virginia |
| Correspondent: | Click to Email |
A variety of dissociative sticking coefficients (DSCs) were measured for alkanes varying in size from methane to nonane on Pt(111) using an effusive molecular beam technique. Thermal equilibrium (Tg = Ts) and non-equilibrium (Tg ≠ Ts) DSC measurements provided information about the gas-surface reactivity and energy transfer. Angle-resolved DSCs, S(700 K; ϑ), measured for methane, ethane, and propane on Pt(111) were used to define thermal DSCs, S(T), and discern dynamical behavior. Methane and ethane DSCs were sharply peaked around the surface normal and were found to have similar dynamical biases away from statistical behavior. Precursor-mediated microcanonical trapping (PMMT) models were used to both analyze and predict DSCs over a wide range of experimental conditions and experiments. It was found that the activation energy for dissociative chemisorption of an alkane scales linearly with its molecular desorption energy from the physisorption well in front of the surface. The molecular desorption energy should be proportional to the van der Waals stabilization energy for the products of dissociative chemisorption. The gas-surface energy transfer increased as the alkane size increased from C1 to C9. For alkanes larger than C4, the gas-surface energy transfer was apparently sufficient to fully thermalize the impinging molecule to the temperature of the surface before reaction such that, S(Tg=300K,Ts) = S(T).