Abstract
Abstract CO adsorption on Pt(111) is investigated by means of thermal He scattering. The relation between the relative height of the He specular peak and the coverage (θ = n CO n Pt ) is approximated well by an exponential at low coverages (θ I I 0 = exp(−18.5θ) for 63 meV He atoms incident at 40°. This relationship is used to monitor the CO coverage throughout this paper. The activation energy for CO desorption has been found to decrease linearly with increasing coverage up to θ ≈ 0.13, i.e. E d = E d 0 − ϵθ , where E do = 133 kJ/mol and ϵ = 68.5 kj/mol. The preexponential factor for desorption is about 1.4 × 10 14 s −1 at T s = 400 K. This set of three parameters allows a fully consistent description of the CO adsorption, desorption and equilibrium measurements.
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