Doctoral Dissertations

Sangeeta Sur

Keywords and Phrases

Inelastic scattering; O3-Ar; Quantum dynamics; MCTDH; Potential energy surface; L-IMLS method; Rovibrational bound states

Abstract

"The observation of larger-than-expected concentrations of heavier isotopologues of ozone known as 'ozone isotopic anomaly' in the stratosphere is a mass-independent effect (in contrast to most kinetic isotope effects familiar to chemists) that is traced back to the recombination process in the formation of ozone in the Chapman cycle. Understanding the relative efficiencies (often approximated as equal for different isotopologues) of the stabilization step (some of the details of which are still a mystery) which involves energy transfer from a highly excited ozone molecule to a third body, M (argon atom in this case) to form stable ozone is a possible path to insight into the phenomenon.

This research discusses theoretical studies of the energy transfer mechanism of the stabilization step. A potential energy surface (PES) is constructed with an electronic structure method that best describes the electronic energy of the O3-Ar complex as a function of its geometry, with which the dynamics of this process is studied. Isotopic substitution of O3 is necessary to study the anomaly. The PESs for the isotopologues: 16O18O16O-Ar and 16O16O18O-Ar are also constructed by straightforward transformation of the coordinate system (no new electronic structure data was needed). The spectroscopy and scattering of 16O16O16O-Ar and its isotopologues are studied using the developed PES for the complex to gain insight into the process.

There is roughly a doubling of the density of allowed quantum states observed for the asymmetric 16O16O18O-Ar isotopologue compared to 16O16O16O-Ar and 16O18O16O-Ar owing to slight change in masses reflecting in the rotational constants, quantum nuclear spin statistics of bosons and symmetry rules. The total rate for 16O16O18O-Ar is also higher than 16O16O16O-Ar due to small changes in the reduced mass of the collision system. With ozone being formed and destroyed continuously in the stratosphere, a small bias could lead to the accumulation of a favored isotopologue"--Abstract, page iv.

Advisor(s)

Dawes, Richard

Committee Member(s)

Grubbs, Garry S.
Winiarz, Jeffrey G.
Woelk, Klaus
Zhang, Yanzhi

Department(s)

Chemistry

Degree Name

Ph. D. in Chemistry

Sponsor(s)

National Science Foundation (U.S.)

Comments

This work was supported by the US National Science Foundation (No. CHE-1566246).

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2020

Journal article titles appearing in thesis/dissertation

  • Development of a potential energy surface for the O₃-Ar system: Rovibrational states of the complex
  • Rotationally inelastic scattering of O₃-Ar: State-to-state rates with the MultiConfigurational Time Dependent Hartree method

Pagination

xi, 102 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2020 Sangeeta Sur, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11692

Electronic OCLC #

1164778116

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Included in

Chemistry Commons

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