Identifying trapping desorption in gas-surface scattering

Classical trajectory simulations are used to determine the energy transfer distribution function P(E-f) for Ne-atoms scattering off the n-hexylthiolate self-assembled monolayer (SAM)/Au{1 1 1} surface. The form of P(E-f) depends on the angles at which it is measured. Though trapping desorption is insignificant for this system, backward scattering and scattering normal to the surface give rise to a unimodal P(E-f) in excellent agreement with the Boltzmann distribution. Forward scattering at large polar angles is bimodal with a Boltzmann-like component. These simulation results show that a Boltzmann component in P(E-f) does not necessarily correspond to a trapping desorption intermediate. (C) 2000 Elsevier Science B.V. All rights reserved.