INFLUENCE OF SUBSTRATE ELECTRONIC EXCITATION ON ATOMIC TRAJECTORIES AND MOLECULAR DISSOCIATION DYNAMICS IN SURFACE SCATTERING UNDER GLANCING INCIDENCE CONDITIONS

Large translational energy losses are generally observed when fast ato mic or molecular beams (either neutral or ionized) are scattered from crystal surfaces under glancing angles of incidence. At keV beam energ ies, these losses can be of order 1 eV/Angstrom, or 1 eV/fs of the tra jectory in the vicinity of the turning point, and are believed to be d ominated by electron-hole pair excitation of the electron-gas. Also, e lectron translational factors must be considered when describing the p rojectile-surface interaction at keV beam energies. We propose that th e ''hot'' electrons associated with both these effects can influence t he particle trajectory, and in the case of molecular projectiles, the dissociation dynamics, by causing quantum mechanical fluctuations in t he occupation of projectile resonances lying energetically above the F ermi-level. The magnitude of this influence is estimated for atomic pr ojectiles using a generalization of the time-dependent Anderson-Newns Hamiltonian. The possibility via this mechanism of transient adsorptio n of the beam while retaining some memory of tile initial beam normal energy is discussed.