Figure 1. Scheme of the barriers considered. The barrier for the desorption (EDes ) and the barrier
for the indirect dissociation (EIndDiss ), represented as thick black lines are referred to the energy
of the adsorption state. The entrance channel barrier for the molecular adsorption (Eent ) and the
exit channel barrier for the dissociative chemisorption (Eext ), represented as red dash lines, are
referred to the asymptotic energy.