Scattering of water from graphite: simulations and experiments

Abstract

The scattering of water molecules from a graphite (0001) surface has been studied experimentally and using molecular dynamics simulations. Model potentials for the gas–solid interaction have been developed and tested by comparing experimental and simulated angular distributions for different translational energies (0.09–0.8 eV), incident angles (30–75°) and surface temperatures (300–1200 K). Good agreement is found for both scattering intensities and angular resolved average velocities, supporting the main features of the model potentials. The importance of trapping at low incident energy is discussed as well as the possibility of vibrational excitation at high collision energy. The latter phenomenon is investigated using purely classical trajectory calculations, a forced oscillator model and a wavepacket propagation scheme. The results indicate that meaningful estimates of the vibrational excitation can be obtained using classical simulations, supporting previously reported results on the CF 3Br/graphite system [M.B. Någård, N. Marković, J.B.C. Pettersson, J. Chem. Phys. 109 (1998) 10350].