Doctoral Dissertations

Jong Yeon Lim

Date of Award

5-1996

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Stuart B. Elston

Committee Members

Robert Compton

Abstract

Doubly differential convey electron emission peaks observed in experiments measuring the angular and energy distribution of electrons produced in ion-atom collisions and in grazing interactions of fast ions with atomically clean surfaces are presented by means of 2-dimensional non-linear fits to model functions. Experimental results for the multipole content of convoy "cusp" peaks for ion-atom collisions at relatively low energies are combined with previous results from the higher collision energy region to access the quality of various Bom approximation approaches to calculation of the cross section. Inclusion of high-order multipoles for ion-solid foil collisions is made to demonstrate the significance of the transition from single- to multi-step collision production mechanisms. For grazing angle ion-surface collisions, results of efforts to develop reasonably simple, yet physically meaningful model functions that permit unbiased comparisons of the extracted convoy peak from the experimental electron distribution are also presented. Experimental results for 0.3 - 0.5 MeV/u carbon ions at grazing angles of 0.1 -1.0 degree with a Si(100) crystal are compared to those of other collision systems. Acceleration as well as broadening of die convoy electron peak due to the dynamic image potential, ot "wake" potential near the surface are observed in triply differential electron emission distributions.

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