State-to-state quantum dynamics of H₂O/HOD scattering from Cu(111): Mode- and bond-selective vibrational energy...

Molecular scattering at solid surfaces has been a sensitive probe of the molecule-surface interaction. Existing theoretical studies have primarily focused on diatomic molecules scattering from metal surfaces. Here, we investigate the vibrational state-to-state scattering dynamics of H₂O/HOD from Cu(111) by a fully coupled six-dimensional quantum dynamical model based on a first-principles determined potential energy surface. Specifically, state-to-state scattering probabilities of H₂O(1ν₁) and HOD with its O-H or O-D excitation are obtained in a wide range of incidence energies. We find very efficient ν₁-to-ν₃ vibrational energy redistribution of H₂O, with a similar efficiency to what we found previously for ν₃-to-ν₁ energy flow in H₂O(1ν₃) scattering. In comparison, we find that the energy transfer from the more localized 1ν_OH or 1ν_OD state to the other bond is much more difficult, in line with the strong bond selectivity observed in the dissociation of HOD on Cu(111). These results suggest that vibrational energy transfer in H₂O/HOD scattering from Cu(111) is mode- and bond-selective, which is better described in the sudden limit via a local mode picture. Implications of these results on the mode-specific vibrational energy transfer of other polyatomic molecules scattering from metal surfaces, such as methane and ammonia, have been discussed. We hope that our study will inspire more quantum state-resolved experiments on state-to-state scattering of polyatomic molecules at metal surfaces.