Vibrational energy transfer at surfaces: The importance of non-adiabatic electronic effects.

Here we review experimental and theoretical work on vibrational energy transfer in collisions of molecules with surfaces. We focus on metal surfaces and on the role of non-adiabatic electroni c transitions in these collisions. Non- adiabatic electronic trans itions contribute to vibrational excitation via the decay of thermally excited electron–hole pairs; conversely, vibrational relaxation can effectively couple vibrational excitation to the production of excited electron– hole pairs. In the case of low work function surfaces, the hot electrons can be observed directly as Vibrationally Promoted Electron Emission (VPPE). The energy distributions of VPEE, and comparison of results on vibrational excitation and relaxation to kinetic models and to ab i nitio theories all indicate that the non- adiabatic coupling is strong and cannot be properly described by perturbative, weak coupling description. A recently developed model based on ab initio potentials and non-adiabatic couplings and on the Independent Electron Surface Hoping (IESH) model is quite successful in describing bot h vibrational excitation and relaxation for NO collisions with Au(111) within th e same theoretical framework