Survival mechanism for rotational rainbows in highly attractive molecule-surface systems: NO scattering from Pt(111)

Rotational rainbow scattering has been observed for NO from Pt (111) at translational energies considerably smaller than the NO-Pt well depth (1 eV). Rotational distributions at superspecular angles show a clear rotational rainbow but scattering towards the surface normal is well described by a Boltzmann distribution. At incoming energies in the order of the well depth, rotational distributions at all angles appear statistical, with an apparent temperature far exceeding the surface temperature, reflecting the energy randomization expected for scattering via a deep well. Orientation-selective trapping caused by the highly directional interaction of NO with the Pt surface restricts the influence of the attractive well on direct scattering at low energies.