Interaction of atomic hydrogen with the graphite single-crystal surface

The reaction of atomic hydrogen (or atomic deuterium) with highly orientated pyrolytic graphite surfaces has been studied by means of thermal desorption spectroscopy. In some cases atomic deuterium instead of atomic hydrogen, was used solely to assign the desorbed masses unambiguously to the different hydrocarbons. The desorption of D₂ and fourteen hydrocarbons was observed. D₂ desorbed at higher temperatures than the CH-(CD) compounds, the desorption spectra of the hydrocarbons contained two peaks. The dependence of the desorption spectra of several hydrocarbons on the heating rate, the atomic hydrogen exposure and the composition of the desorption products was investigated in detail. The kinetic parameters of the desorption process were determined for CH, C₂H₂, and CD₄. The spectra showed that there must be a first order desorption process for all the hydrocarbons, the values for the activation energy and the frequency factor were the same within experimental errors. The results were discussed by means of a simple model.