MOLECULAR-DYNAMICS SIMULATION OF THE H-2 RECOMBINATION ON A GRAPHITE SURFACE

This article reports a model study aimed at the detailed description o f the mechanism of formation of molecular hydrogen onto dust grain sur faces in the interstellar medium. Using classical trajectories (CT) an d quasi-classical trajectories (QCT) calculations, the H-2 recombinati on from the Eley-Rideal process has been studied. This reactive proces s, involving the collision between one gas phase atomic hydrogen and o ne other H atom previously chemisorbed on a graphite surface, could be an efficient mechanism to explain the formation of H-2 in the interst ellar medium. Two empirical potential models have been used to extract the main physical and chemical properties of this system. The efficie ncy of the recombination process has been analysed as a function of th e collision energy and also as a function of the H coverage on the gra phite surface. From an energetic point of view, the newly formed H-2 m olecules have been found to be desorbed with a large translation kinet ic energy and also in highly excited vibrational states.