Surface processes involving nitrogen molecules and atoms on silica surface at low temperature: the role of energy exchanges

The dynamics of elementary surface processes, promoted by nitrogen atoms and molecules impacting a silica surface, has been investigated by adopting a semiclassical scattering method. The appropriate treatment of the long-range interaction forces emphasized the crucial control exercised by the weakly bound precursor state on the stereo-dynamics of all basic elementary processes occurring at the gas-surface inter-phase. Molecular dynamics simulations have highlighted the role of vibrationally excited molecules in plasma dynamics. Indeed, N2 molecules, impinging the surface in low-medium vibrational levels, conserve the initial vibration state while are inelastically scattered, rotationally excited and translationally colder. Moreover, N2 molecules nascent from the atomic recombination on the surface have a fair probability of forming at very high vibrational levels, with a consistent part of reaction exothermicity transferred to the translational energy. Consequently, the surface induces a strong non-equilibrium condition, influencing directly the dynamics of processes occurring in the plasma bulk.