Time-dependent quantum mechanical calculations on the formation of molecular hydrogen on a graphite surface via an Eley-Rideal mechanism

The associative desorption of H-2 (v,j) on a graphite (0001) surface via an Eley-Rideal mechanism has been studied theoretically. In our calculations we used a time-dependent wave packet method treating three degrees of freed om quantum mechanically. A newly developed potential energy surface based o n plane-wave density functional calculations was employed. In our 3D calcul ations we find less vibrational excitation for the product H-2 molecules th an in calculations that used only two degrees of freedom. However, the prod uct H-2 molecules are formed rotationally excited. This could have importan t implications for the chemistry of H-2 in the interstellar medium and the interpretation of astronomical data.