surface model, illustrating the two azimuthal orientations used for reactivity measurements. For parallel incidence , the incident methane impinges on the surface along the direction, parallel to the direction of the missing rows. For perpendicular incidence , is incident along the  direction, perpendicular to the missing rows and to the main surface corrugation. The first, second, and third layer atoms are differentiated from bulk with green, blue, and red colors, respectively.
Laser-off reactivity, , for on , at and 600 K, as function of translational energy at normal incidence : (◼,◻) , pure and mixtures, ; (▼) mixture, . The solid and dashed lines are S-shaped curves fitted to the data points.
State-resolved reactivities and for on as a function of incident translational energy (normal incidence, ) for .
Comparison of translational energy scaling models: (●) and (▲) measured for normal incidence. (Other symbols) State-resolved reactivities measured for off-normal incidence as a function of (local) normal energy calculated by different models. To ease comparison of different scaling models, we use a normalized translational energy scale (see text).
and for on at fixed incident translational energy as a function of polar angle for incidence parallel and perpendicular to the missing row direction.
Relative area, calculated in the 3D shadowing model, of the first three Pt layers on exposed to the molecular beam as a function of polar angle for incidence parallel and perpendicular to the missing row direction.
Reactivity ratio for and as a function of polar angle of incidence , compared to predictions of the 3D shadowing model assuming reaction only on the first layer ridge atoms.
reactivity enhancement as a function of polar angle for incidence perpendicular and parallel to the missing row directions.
Laser-off reactivity for on (open squares) and Pt(111) (closed circles) as a function of incident translational energy (normal incidence) for . S-shaped curves are fitted to the data to extract a difference in average barrier height of .
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