Theoretical Studies of Chemical Reaction Dynamics

Citation

Klippenstein, Stephen Jacob (1988) Theoretical Studies of Chemical Reaction Dynamics. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/dbrd-wj15. https://resolver.caltech.edu/CaltechTHESIS:03062013-161416978

Abstract

In this thesis theoretical models a.re developed and/or applied to the study of the dynamics of a variety of chemical reactions. First, a semiclassical model is developed to describe the effect of mutual orientation of the donor and acceptor on the rate of electron transfer between two large aromatic groups. The next reaction considered is that of gas phase H-atom transfer reactions. In this case a comparison is made of two previously developed approximations for the treatment of the particular case of H-atom transfer between two heavy particles.

The next topic involves the study of the rate of intramolecular vibrational redistribution of energy. First, an iterative procedure is developed for determining more and more accurate effective Hamiltonians for the description of the dynamics. The foundation of this method is the separation of the basis states into resonant and nonresonant sets followed by an adiabatic approximation for the dynamics of the off-resonant set. A second study involves the application of artificial intelligence techniques to the choice of a small set of basis states which are the states of greatest importance to the redistribution dynamics.

The remainder of the thesis is devoted to the study of those unimolecular dissociation/free radical recombination reactions which contain highly flexible transition states. For these reactions, a method for determining the quantum partition function for the transition state in terms of path integral ratios is developed and applied to the study of the thermally activated methyl radical recombination. Subsequently, a method is developed for determining the number of states, for the transition state, at a given energy and angular momentum. The basis of the method is the use of conventional Euler angle coordinates in the Monte Carlo evaluation of phase space integrals. This method is applied to the NCNO, CH₂CO, and H₂O₂ photodissociation processes. Also presented is a discussion of both the trend of the location of the transition state with increasing energy and the possible influence of excited potential energy surfaces.

Thesis Files