Dynamics of H2 formation on a graphite surface

We have studied the dynamics of energy-rich H2 produced on a graphite surface in H(ad) + H(g) using a classical trajectory procedure. The majority of H(g) recombine with H(ad) on a subpicosecond timescale with a significant portion of the reaction exothermicity depositing in the H2 vibration, leading to a vibrational population inversion. Vibrational excitation is strong when H(g) first approaches close proximity of the surface and rebounds toward H(ad) in a direct-mode mechanism. H(g) reaching close to the surface at large impact parameter tends to become trapped before rebounding to abstract H(ad), a complex-mode mechanism.