Abstract
We report the results of inelastic differential scattering experiments and full-dimensional molecular dynamics trajectory simulations for 2.76 eV H atoms colliding at a surface of solid xenon. The interaction potential is based on an effective medium theory (EMT) fit to density functional theory (DFT) energies. The translational energy-loss distributions derived from experiment and theory are in excellent agreement. By analyzing trajectories, we find that only a minority of the scattering results from simple single-bounce dynamics. The majority comes from multibounce collisions including subsurface scattering where the H atoms penetrate below the first layer of Xe atoms and subsequently re-emerge to the gas phase. This behavior leads to observable energy-losses as large as 0.5 eV, much larger than a prediction of the binary collision model (0.082 eV), which is often used to estimate the highest possible energy-loss in direct inelastic surface scattering. The sticking probability computed with the EMT-PES (0.15) is dramatically reduced (5 × 10–6) if we employ a full-dimensional potential energy surface (PES) based on Lennard-Jones (LJ) pairwise interactions. Although the LJ-PES accurately describes the interactions near the H–Xe and Xe–Xe energy minima, it drastically overestimates the effective size of the Xe atom seen by the colliding H atom at incidence energies above about 0.1 eV.
Highlights
Collisions of atoms and molecules with surfaces typically lead to two experimentally identifiable outcomes: direct inelastic scattering (DIS) and trapping followed by thermal desorption (TD).[1]
For the Molecular dynamics (MD) simulations with our effective medium theory (EMT)-potential energy surface (PES), we modeled Xe as a (6 × 6) 6-layered slab with periodic boundary conditions
The minimum energy structure represented by the PES corresponds to H atoms adsorbed at an fcc hollow where the H atom is 2.8 Å displaced toward the vacuum from the plane defined by the equilibrium positions of the first layer of Xe atoms
Summary
Collisions of atoms and molecules with surfaces typically lead to two experimentally identifiable outcomes: direct inelastic scattering (DIS) and trapping followed by thermal desorption (TD).[1]. This may involve surface penetration followed by resurfacing.[11,12]
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