Date of Award

Winter 1993

Project Type

Dissertation

Program or Major

Chemistry

Degree Name

Doctor of Philosophy

First Advisor

Howard Mayne

Abstract

In this dissertation we examine rotationally inelastic collisions involving an atom plus a diatom. We concentrate specifically on the Ar + HF system. In these investigations we employ a number of theoretical methods, including classical trajectories, quantum close-coupled calculations and semiclassical methods, to examine the differential cross sections in Ar + HF. We also investigate the effects of various "sudden" approximations on the scattering dynamics and the limitations of these approximations.

Through this work we were able to identify a new quantum feature in rotationally inelastic scattering. By studying the time evolution of transition amplitudes (rather than probabilities) we are able to ascribe this feature to a balance between the attractive and repulsive parts of the potential energy surface governing the collision system. We propose that this feature will be a general scattering feature in systems with a potential that has substantial repulsive anisotropy and a significant attractive well.

We present a classical trajectory method for direct simulation of a scattering experiment. We use this method to calculate laboratory frame differential cross sections for rotationally inelastic scattering in the Ar + HF system. We find that the results of this method are in excellent agreement with more standard approaches for the comparison of theoretical to experimental results.

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