Formation of molecular hydrogen on a graphite surface via an Eley–Rideal mechanism

The associative desorption of hydrogen atoms on graphite via an Eley–Rideal mechanism is studied theoretically. Time-independent quantum reactive scattering calculations are performed on a potential energy surface calculated using the generalised gradient approximation of density functional theory. The absence of a barrier to reaction leads to a reaction probability which is close to one, even for low collision energies. The vibrational product distribution of H2 shows a peak in the (v=2) vibrational state with appreciable population of higher states. The significance of these results for chemistry in the interstellar medium is discussed.