Studies of rotationally inelastic collisions in argon + hydrogen fluoride

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