Noroski, Joseph H.
(2009)
COLLISION ENERGY DEPENDENCE OF THE REACTIONS OF METASTABLE NEON WITH SMALL MOLECULES.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
The reaction dynamics of Ne* (2p⁵3s³P₂, ³P₀) + X → [NeX]⁺ + e⁻(X = H₂, CO, N₂, NO, O₂, CO₂, and C₂H₂) were studied with supersonic beams at various collision energies (E) via electron spectroscopy. Increasing E decreases the interparticle distance at which ionization occurs, allowing for exploration of the reaction potential energy surfaces via the kinetic energy ε of the ejected electron. Data were fit to give vibrational populations and line shifts (Δεs), the difference between the excitation energy of Ne* and the vibronic energy of the target molecules, where vibronic excitation is due to Ne*. The resulting populations were compared to calculated or experimental Franck-Condon factors (FCfs), and vibrational progressions were identified. Deviation from Franck-Condon (FC) behavior was observed in all cases except for C₂H₂, and all spectra at all E showed a blue shift except CO₂. With increasing E, Δεs for H₂⁺, CO⁺, and N₂⁺ increased with increasing E, while Δεs decreased for NO⁺ and C₂H₂⁺. The CO2⁺ spectra revealed a nearly constant red shift for the lowest three E and a blue shift for the highest E. O₂⁺ showed a very small blue shift, but the O₂⁺ populations were not determined due to an underlying continuum. Penning, excitation transfer, and ion-pair mechanisms are the most widely accepted for the reactions of metastable atoms. The closed-shell structure of H₂, CO, and N₂ and the large, increasing Δεs suggest that their Ne* reactions proceed via the Penning mechanism. The open- shell structure of NO and its decreasing Δεs indicates changing dynamics and possibly also competition between all three mechanisms for Ne* + NO. The very small Δεs for O₂⁺ implies the excitation transfer mechanism for Ne* + O₂. Ne* reactions with CO₂ and C₂H₂ both exhibited constant Δεs values for more than one E. This suggests that an excitation transfer mechanism is at work in these systems, but changes in Δεs at other E indicate that competing mechanisms may also be relevant. Lastly, a retrospective on authoring a solutions manual for a freshman chemistry textbook is offered.
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| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
17 June 2009 |
| Date Type: |
Completion |
| Defense Date: |
3 April 2009 |
| Approval Date: |
17 June 2009 |
| Submission Date: |
17 April 2009 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
autoionization; electron spectroscopy; metastable neon; molecular collisions; Penning ionization; reaction dynamics |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-04172009-114939/, etd-04172009-114939 |
| Date Deposited: |
10 Nov 2011 19:38 |
| Last Modified: |
15 Nov 2016 13:40 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/7259 |
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