Selectivity and Stereodynamics Effects in the Scattering of Nitrogen Molecules from a Graphite Surface

The scattering of N2 molecules from a graphite surface was studied by Molecular Dynamics simulations, based on a state-to-state semiclassical collisional method, and in conjunction with a new reactive Potential Energy Surface that includes the long-range part describing properly, for all accessible molecular configurations respect to the surface, the non-covalent interactions promoting the physisorption. Molecules in well-defined initial internal vibrational and rotational states (vi, ji) impinge on the surface with collisional energy (Ecoll) covering the range from thermal (0.01eV) up to hyperthermal values (2.0eV). In addition to the ground-state of ortho and para symmetry, nitrogen molecules excited initially in low-medium vi and ji levels have been also considered. The main features of scattering dynamics, already reported in the literature, are confirmed on a larger range of both initial rotational levels and collision energies. However, new selectivity and stereodynamics effects are highlighted by studying in detail the microscopic mechanisms driven by the interaction that promotes physisorption. This investigation contributes also to a broader understanding of molecular scattering from surfaces by relating observed effects to phenomena controlled by rotational alignment and rotational rainbow, already well characterized, both experimentally and theoretically, in gas-phase collisions and for molecular scattering from metallic surfaces.