Mean-Field Techniques for Atomic Collision Theory (Physics)

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Initial application of mean-field theory to atomic collisions has indicated that it handles well some of the difficulties encountered in basis expansion techniques for ion- atom scattering. Some of the strengths of the theory are (i) that it provides intuitive pictures for model development and mechanism elucidation, (ii) the ease with which continuum intermediate states are included, and (iii) the fact that many- body effects are included in the transition matrix elements. Since the initial results were so encouraging, it is proposed to broaden the generality and scope of this technique to make it applicable to a wider variety of problems. A proper framework has been developed and tested to provide instantaneous coupling from the quantum electronic degrees of freedom to the classical nuclear degrees of freedom. When this has been incorporated into the ion-atom collision program, and some three-dimensional capability has been developed, it will be possible to address a variety of topics such as chemical reactions and ion-surface scattering, in addition to problems in low-energy (adiabatic) ion-atom charge exchange. This research group will apply its well-established techniques for numerical solution of the time-dependent Schrodinger equation to obtain a better understanding of the interaction between an atom or ion and a metal surface. The objective of the proposed work is to bring together state-of- the-art descriptions for the time-dependent behavior of the atom (TDHF), the trajectory (CQC) and the surface (jellium) to obtain the best available description of atom-surface interactions. The group is uniquely qualified to make significant contributions to charge exchange scattering from surfaces in a relatively short time. This research effort should provide reliable values for some of the parameters used in current models, guidance as to the range of validity of certain models, and intuitive pictures for thinking about the atom-surface interaction.