The compensation effect in thermal desorption of adsorbate systems with lateral interactions

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Abstract
Within the Polanyi–Wigner model of thermal desorption, lateral interactions are revealed by a coverage-dependent activation energy of desorption E(θ) and a preexponential factor ν(θ). Several experiments have shown that ν and E often satisfy the ‘‘compensation effect’’ ln ν(θ)=E(θ)/RTc+const. In this contribution we introduce this compensation effect into the rate expression for thermal desorption and present calculated thermal desorption spectra assuming pairwise lateral interactions and first- or second-order desorption kinetics. The results emphasize that simplified thermal desorption spectroscopy analysis procedures based on peak maximum temperatures and peak widths only will almost always lead to incorrect results.

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