Scattering of water from graphite: simulations and experiments

The scattering of water molecules from a graphite (0001) surface has been s tudied experimentally and using molecular dynamics simulations. Model poten tials for the gas-solid interaction have been developed and tested by compa ring experimental and simulated angular distributions for different transla tional energies (0.09-0.8 eV), incident angles (30-75 degrees) and surface temperatures (300-1200 K). Good agreement is found for both scattering inte nsities and angular resolved average velocities, supporting the main featur es of the model potentials. The importance of trapping at low incident: ene rgy is discussed as well as the possibility of vibrational excitation at hi gh collision energy. The latter phenomenon is investigated using purely cla ssical trajectory calculations, a forced oscillator model and a wavepacket propagation scheme. The results indicate that meaningful estimates of the v ibrational excitation can be obtained using classical simulations, supporti ng previously reported results on the CF3Br/graphite system [M.B. Nagard, N . Markovic, J.B.C, Pettersson, J. Chem. Phys. 109 (1998) 10350]. (C) 1999 E lsevier Science B.V. All rights reserved.