On the Influence of Transitions Between Distinct Adsorption States on the Desorption Kinetics of Molecules

A model is proposed for desorption of molecules via a precursor state in the presence of two distinct chemisorption states on the surface. Analytical expressions describing the temporal evolution of the concentration of molecules in chemisorbed states are obtained. It is shown that redistribution of molecules between the chemisorbed states can lead to a non-monotonic time dependence of the concentration of molecules in one of the states in the early stages of desorption, as well as to a significant change in the spectra of temperature programmed desorption.