Surface diffusion of n-alkanes on Ru(001)

The surface diffusion of n-alkanes on Ru(001) was measured using laser-induced thermal desorption (LITD) techniques. The surface diffusion coefficients for propane, n-butane, n-pentane, and n-hexane all displayed Arrhenius behavior. The surface diffusion activation energies increased linearly with carbon chain length from Edif =3.0±0.1 kcal/mol for propane to Edif =4.8±0.2 kcal/mol for n-hexane. In contrast, the surface diffusion preexponentials remained nearly constant at D0 ≂0.15 cm2 /s. Measurements performed at different coverages also revealed that the surface diffusion coefficients were coverage-independent for all the n-alkanes on Ru(001). The surface corrugation ratio Ω was defined as the ratio of the diffusion activation energy to the desorption activation energy, Ω=Edif /Edes . The surface corrugation ratio was observed to be remarkably constant at Ω≂0.3 for all the n-alkanes. This constant corrugation ratio indicated a linear scaling between the diffusion activation energy and the desorption activation energy. This behavior also suggested that the n-alkanes move with a rigid configuration parallel to the Ru(001) surface.