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Time-resolved studies of molecular reaction dynamics and development of experimental methodology

Citation

Scherer, Norbert Franz (1989) Time-resolved studies of molecular reaction dynamics and development of experimental methodology. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-11302006-091037

Abstract

The six research topics presented in the following chapters are concerned with several diverse problems of molecular reaction dynamics in isolated gas-phase environments. The scope of the studies ranges from performing direct measurements of bond-breakage on electronically dissociative potential energy surfaces, to monitoring the time-course of a restricted geometry bimolecular reaction. The common experimental method used in all of the studies has been a variant of pump-probe time-resolved spectroscopy. The underlying theme of the endeavors has been threefold: 1) To gain a better understanding of the role of intramolecular dynamics that precede or are commensurate with the reaction dynamics; 2) To begin to appreciatiate the observable manifestations of specific features of the reactive potential energy surface; and 3) To utilize the specific temporal behavior to elucidate quantitative information for the said potential surface.

The studies of molecular dissociation on repulsive electronic surfaces has lead to a quantification of the timescale for primary steps in reaction processes. Moreover, transform limited temporal/spectral studies have begun to focus on specific long-range reaction fragment interactions in a state-specific manner. The latter endeavor has identified a mechanism for the reaction-fragment(s) interaction in the near-asymptotic product region.

Predissociative reaction and intramolecular dynamical behavior has been studied on ground potential energy surfaces. Overtone excitation of the OH-stretch mode of hydrogen peroxide enables molecular ground state excitation and state-specific detection of the OH reaction product. These investigations point out the potential of this picosecond pump-probe method for directly elucidating the intramolecular energy redistribution process and the possibility for direct investigation of the long-range tail region of the free-radical recombination potential surface.

The investigation of a spatially oriented bimolecular reaction has conclusively shown that the IH-OCO reaction proceeds by way of the [HOCO] reaction complex species. The close proximity of the van der Waals bound reactants produces unique multi-body interactions not found in the gas phase but which may arise in condensed phases. Moreover, these investigations have obtained evidence for a unique reaction reasonance (which is analogous to a shape-resonance) feature. The presence of such a resonance in the reaction entrance channel region affects the temporal behavior and yield of product formation.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Zewail, Ahmed H.
Thesis Committee:
  • Unknown, Unknown
Defense Date:23 January 1989
Author Email:nfschere (AT) uchicago.edu
Record Number:CaltechETD:etd-11302006-091037
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-11302006-091037
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4693
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:18 Dec 2006
Last Modified:26 Dec 2012 03:11

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