Formation of vibrationally excited hydrogen molecules on a graphite surface

We study the recombination of hydrogen atoms on graphite grains in the limits of strong and weak interactions using a trajectory procedure. In the limit of strong gas–surface interaction dominated by chemisorption energies, the total reaction cross-section is 0.375 Å2 and the vibrational energies of H2(g) distribute between v=0 and 3. When the interaction is a Van der Waals type, σ is found to be as large as 17.4 Å2 and in this weak interaction limit, most of the reaction exothermicity is carried away by the vibrational motion of H2(g) producing strong excitation.