University of Illinois Urbana-Champaign

Photodissociation Dynamics Of Ch2oo On Multiple Potential Energy Surfaces: Experiment And Theory

Esposito, Vincent J.

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WH02_1.pptx
5849.pdf

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https://hdl.handle.net/2142/116534

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Title
Photodissociation Dynamics Of Ch2oo On Multiple Potential Energy Surfaces: Experiment And Theory
Author(s)
Esposito, Vincent J.
Contributor(s)
  • Lester, Marsha
  • Karsili, Tolga N. V.
  • Marchetti, Barbara
  • Bush, Rachel E.
  • Bush, Sarah A.
  • Werba, Olivia
  • Antwi, Ernest
  • Vansco, Michael F.
  • Caracciolo, Adriana
  • Wang, Guanghan
  • Liu, Tianlin
Issue Date
2022-06-22
Keyword(s)
Mini-symposium: Spectroscopy meets Chemical Dynamics
Abstract
Criegee intermediates are zwitterionic carbonyl oxide species that result from alkene ozonolysis in the Earth's troposphere. UV excitation of the simplest Criegee intermediate, CH$_{2}$OO, across most of the broad span of the (B $^{1}$A$^{\prime}$) - (X $^{1}$A$^{\prime}$) spectrum results in prompt dissociation to two energetically accessible asymptotes: O ($^{1}$D) + H$_{2}$CO (X $^{1}$A$_{1}$) and O ($^{3}$P) + H$_{2}$CO (a $^{3}$A$^{\prime \prime}$). Dissociation proceeds on multiple singlet potential energy surfaces that are coupled by two regions of conical intersection (CoIn). Velocity map imaging studies reveal a bimodal total kinetic energy (TKER) distribution for the O ($^{1}$D) + H$_{2}$CO (X $^{1}$A$_{1}$) products. The unexpected low TKER component corresponds to highly internally excited H$_{2}$CO (X $^{1}$A$_{1}$) products. Full dimensional trajectory calculations suggest that the bimodal TKER distribution of the O ($^{1}$D) + H$_{2}$CO (X $^{1}$A$_{1}$) products originates from two different dynamical pathways: a primary pathway evolving through one CoIn region to products and a smaller component sampling both CoIn regions during the dissociation process. Those that access both CoIn regions likely give rise to the more highly internally excited H$_{2}$CO (X $^{1}$A$_{1}$) products. The remaining trajectories dissociate to O ($^{3}$P) + H$_{2}$CO (a $^{3}$A$^{\prime \prime}$) products after traversing through both CoIn regions. No trajectories follow the more thermodynamically favorable spin-forbidden pathway to O ($^{3}$P) + H$_{2}$CO (X $^{1}$A$_{1}$) products. This complementary experimental and theoretical investigation provides insight into the photodissociation of CH$_{2}$OO via multiple dissociation pathways through two regions of CoIn that control the branching and energy distributions of products
Publisher
International Symposium on Molecular Spectroscopy
Type of Resource
text
Genre of Resource
Conference Paper / Presentation
Language
eng
Handle URL
https://hdl.handle.net/2142/116534
DOI
https://doi.org/10.15278/isms.2022.WH02
Copyright and License Information
Copyright 2022 held by the authors

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Abstracts & Presentations - 2022 International Symposium on Molecular Spectroscopy PRIMARY