Quantum flux analysis of the scattering of oriented NO molecules from surfaces

We present a time-resolved quantum flux analysis of oriented NO collisions with flat Ag,Pt surfaces. We adopt both the molecular and the adiabatic viewpoints. This enables us to understand the basic mechanisms that allows one to correlate the final steric effects with the initial molecular orientation. We find that rotational excitation is always enhanced (diminished) when the O (N) end of the molecule is initially directed towards the surface, in qualitative agreement with the experimental observations of Kleyn and co-workers. Our simulations illustrate the two limiting regimes of rotational excitation and stereospecificity. One is sudden and implies that the initial orientation is conserved as the molecule strongly interacts with the surface. The other one is adiabatic and includes reorientation effects. The adiabatic description proves to be invaluable in complementing a molecular analysis in surface scattering.