Theoretical Studies of Chemical Reaction Dynamics

Author: Kaye, Jack Alan

Year: 1982

Degree: Dissertation (Ph.D.)

Advisor: Goddard, William A., III

Committee Members: Goddard, William A., III; Kuppermann, Aron; Dervan, Peter B.; Sparks, Randal K.

Option: Chemistry

DOI: 10.7907/vkds-vb56

Abstract

The collinear collision of an atom with a diatomic molecule has been studied within the frameworks of quantum and classical mechanics. Three major topics have been investigated.

In part I, the collinear collision of hydrogen atoms with hydrogen fluoride (and singly deuterium substituted variants of this system) have been studied in the exchange channel by coupled-channel quantum mechanical calculations using a realistic (high barrier) potential energy surface. We have also investigated the effect on the dynamics of varying the barrier height of the potential energy surface.

In part II, we consider the characterization of low energy resonances in the collinear H + H2 and F + H2(HD, DH, D2) systems. A variety of characterization techniques are used; the most useful proves to be the variation with energy of the eigenvalues of the collision lifetime matrix.

In part III, we develop the method of hyperspherical coordinates for the study of collinear reactive atom-diatomic molecule collisions. The method is tested for the H + H2 system, and is applied to a model system above the threshhold for collision-induced dissociation and to reactions in which a light atom (hydrogen) is transferred between two heavy ones. Systems of this type studied include I + HI and Br + HCl; we also consider some aspects of the dynamics in the Cl + HCl system. We develop the formalism to extract the physical scattering wave function from the method and present preliminary results of probability densities and probability current densities on the H + H2 system. We also consider the formulation of the method in the adiabatic representation and examine both numerically and analytically the behavior of the coupling matrices at large values of the propagation variable. Convergence properties of the method are investigated in detail for the H + H2 and F + H2 systems. Quasi-classical trajectory calculations have been used to help understand the results obtained and to determine the importance of quantum mechanical effects.

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