CH4 on various surfaces

Several investigations have been undertaken on a number of metal surfaces in order to elucidate the dynamics and mechanisms behind the direct chemisorption of CH4 at higher kinetic energies. 

A similar study by Schoofs et al. [43] of methane dissociation on the Pt(l 11) surface produced qualitatively similar results An exponential increase in the value of S0 with increasing normal energy and a weak dependence of S0 on surface temperature, Ts. Further, like Rettner et al. [40], Schoofs and coworkers find these trends consistent with a hydrogen tunneling mechanism through a one-dimensional parabolic-shaped activation barrier. 

Similar to the trends seen earlier by Refiner et al. [40] of CH4 on the W(1 1 0) surface, Lee et al. also observed the enhancing effect of vibrational excitation on the direct chemisorption of CH4. From this data, Lee et al. also propose, like Refiner et al., that vibrational energy may be more efficient 

In an attempt to quantify separately the dependence of S0 on translational and vibrational energy, Holmblad et al. modeled the contribution to the sticking probability from vibrationally excited states of methane as an S-shaped curve, as suggested in previous studies [53]. This curve is described by the 

A quantum tunneling mechanism was proposed by Yerhoef et al. to describe these trends, and an attempt was made to develop a tunneling model to predict the chemisorption of methane and ethane over the entire range of normal incident energies studied. This was accomplished by modeling the 

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