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Please use this identifier to cite or link to this item: http://hdl.handle.net/1974/7456

Title: Chemical Reaction Dynamics at the Statistical Ensemble and Molecular Frame Limits
Authors: Clarkin, OWEN

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Keywords: Femtosecond Laser
Coincidence Imaging Spectroscopy
Scattered Light Background Reduction
Dendritic Cupric Oxide
Time Resolved Photoelectron Spectroscopy
Effect of Air Pressure on Laser Performance
Effect of Weather on Laser Performance
Transition state theory
Imaging Valence Electronic Dynamics
Non-Adiabatic Alignment
Time Resolved Photoelectron Angular Distributions
Excited States
Conical Intersections
Molecular Frame
Potential Energy Surfaces
Time Dependent Density Functional Theory
Chemical Reaction Dynamics
Flexible Transition State Theory
Carbon Disulfide
Issue Date: 12-Sep-2012
Series/Report no.: Canadian theses
Abstract: In this work, experimental and theoretical approaches are applied to the study of chemical reaction dynamics. In Chapter 2, two applications of transition state theory are presented: (1) Application of microcanonical transition state theory to determine the rate constant of dissociation of C2F3I after π∗ ← π excitation. It was found that this reaction has a very fast rate constant and thus is a promising system for testing the statistical assumption of molecular reaction dynamics. (2) A general rate constant expression for the reaction of atoms and molecules at surfaces was derived within the statistical framework of flexible transition state theory. In Chapter 4, a computationally efficient TDDFT approach was found to produce useful potential energy surface landscapes for application to non-adiabatic predissociative dynamics of the molecule CS2 after excitation from the ground state to the singlet C-state. In Chapter 5, ultrafast experimental results of excitation of CS2 to the predissociative neutral singlet C-state is presented. The bandwidth of the excitation laser was carefully tuned to span a two-component scattering resonance with each component differently evolving electronically with respect to excited state character during the quasi-bound oscillation. Scalar time-resolved photoelectron spectra (TRPES) and vector time-resolved photoelectron angular distribution (TRPAD) observables were recorded during the predissociation. The TRPES yield of photoelectrons was found to oscillate with a quantum beat pattern for the photoelectrons corresponding to ionization to the vibrationless cation ground state; this beat pattern was obscured for photoelectron energies corresponding to ionization from the vibrationally excited CS2 cation. The TRPAD data was recorded for two general molecular ensemble cases: with and without a pre-excitation alignment laser pulse. It was found that in the case of ensemble alignment (Chapter 6), the “molecular frame” TRPAD (i.e. TRMFPAD) was able to image the purely valence electronic dynamics of the evolving CS2 C-state. The unaligned ensemble TRPAD observable suffers from excessive orientational averaging and was unable to observe the quantum beat. Engineering efforts were also undertaken to eliminate scattered light background signal (Chapter 7, Appendix A) and improve laser stability as a function of ambient pressure (Appendix B) for TRMFPAD experiments.
Description: Thesis (Ph.D, Chemistry) -- Queen's University, 2012-09-11 22:18:20.89
URI: http://hdl.handle.net/1974/7456
Appears in Collections:Chemistry Graduate Theses
Queen's Theses & Dissertations

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