Stereodynamic Effects of CO Molecules Scattered from a Graphite Surface

The scattering of CO molecules from a graphite surface has been characterized by exploiting molecular dynamics simulations, based on a chemical state-to-state semiclassical collisional method, and adopting a new reactive potential energy surface that considers the proper treatment of long-range noncovalent interactions promoting the physisorption. Carbon monoxide molecules impinge the surface in well-defined initial rotovibrational states and with the collision energy varying from subthermal up to hyperthermal values. The simulations predict that scattering events occur through both single- and multi-bounces and the initial vibrational state is preserved. In the multibounces instance, molecules tend to be trapped in the physisorption well, especially for collision energies lower than the thermal one. For medium-high collision energies, the scattering occurs mainly via a singlebounce mechanism. The heteronuclear character of the molecule brings out a new intriguing stereodynamic effect, in addition to those highlighted for homonuclear molecules: due to the anisotropic physisorption attraction, the molecule C-end bends toward the surface while approaching this latter. This effect produces evident propensities in the final rotational distributions of the CO scattered molecules.