Inelastic Scattering of Formaldehyde on Au(111) surface

Inelastic scattering between gas molecules and surfaces is a fundamental process that has been investigated extensively. During this process, the energy exchange between the gas and the surface changes the internal and translational degrees of freedom of the scattered gas molecules. However, the energy transfer mechanism between the molecule and surface is quite complicated and not well understood. In recent gas-surface scattering experiments [Phys. Chem. Chem. Phys. 19, 19896 (2017)] on formaldehyde scattering off the gold surface, the scattered formaldehyde molecules had a high propensity to excite twirling motion about the C-O bond axis. In the work presented here, we used classical dynamics simulation to understand energy transfer in formaldehyde-surface collisions and to probe the mechanism of interconversion of translational energy to rotational energy. Our simulations capture the trend of the experiments for the formaldehyde-Au scattering, both in terms of rotational energy distribution and trapping probabilities, and provide an atomic-level mechanism for the energy transfer process during the scattering process.