Cold, Controlled, Ion-Molecule Reactions

Coulomb crystals in linear Paul ion traps (LIT) have proven to be a fruitful environment to study gas-phase ion chemistry and spectroscopy of molecular ions. Recently, the capabilities of such apparatuses have been extended by (radially) coupling them to a time-of-flight mass spec-trometer (TOFMS). The TOFMS enables simultaneous detection of all constituent masses in the ion trap. Thus, one can follow reactions both by the depletion of reactants, as well as growth of product channels, allowing for a more complete description of reaction kinetics. We have designed, built, and characterized a combined LIT-TOFMS apparatus for the purpose of studying cation-molecule reactions. This thesis provides an overview of ion trapping theory and basic reaction kinetics/dynamics. A detailed description of the apparatus and four ion-molecule reactions are also discussed. The first two ion-molecule reactions covered demonstrate quantum control over laser-cooled Ca+ in the reactions Ca+ + NO and Ca+ + O2. The third ion-molecule reaction elucidates the isomer specific reaction mechanisms observed in the reaction C2H2+ + C3H4. The last reaction covered is CCl+ + C2H2, which reveals new pathways to ionic products important in chemistry of the interstellar medium. The thesis concludes with future prospects to extend the capabilities of the apparatus in pursuit of colder and more controlled ion-molecule reaction studies.
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Department of Physics
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University of Colorado Boulder
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