U.S.-Japan Cooperative Research: Interactions of Swift Charged Particles with Valence Electrons Near Surfaces

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This award provides support for a two year cooperative research project between Professor Joachim Burgdorfer and Professor Stuart B Elston, Department of Physics and Astronomy, University of Tennessee, and the Quantum Physics Group at the Department of Engineering, Kyoto University, Japan, led by Professor Michi-hiko Mannami. The purpose of the project is to undertake a collaborative theoretical and experimental study of the collision interactions of fast charged particles with valence electrons near surfaces. Scattering from clean well defined surfaces at glancing angles provides the opportunity to study collision processes at large impact parameters, thereby accentuating interactions with valence electrons in the proximity of the surface while suppressing contributions from ionic cores. The project will involve firstly a theoretical and experimental investigation of the energy and angular distributions of convoy electrons ejected in glancing angle ion-surface collisions as a function of projectile charge state and velocity, and surface structure and composition. Secondly a computer simulation of the reflection of scattered ions will be developed, with particular emphasis on the simultaneous evolution of electron projectile states and the dynamical response of the valence electron. Finally a theoretical and experimental investigation of the yield and angular distribution of convoy electrons produced by channeled fast ions will be carried out. There is strong overlap between the work of the groups at Kyoto University and the University of Tennessee, with complementing capabilities in both theory and experiment. The group in the US, for example, have extensive numerical experience in Monte-Carlo simulations for electronic transport in solids, where as the Kyoto group have developed a simulation code for ionic scattering from solid surfaces. This project should provide detailed new information on the contribution of delocalized electrons to excitation processes, on the collective response of conduction electrons and its influence on secondary electron emission and, more broadly, on the usefulness of inelastic collision processes as a tool of surface diagnostics.