EXPLORING THE MECHANISM OF THE ELECTRONIC QUENCHING OF NO (A2Σ+) WITH CO2

Bridgers, Aerial

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https://hdl.handle.net/2142/122346 Copy

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Title

EXPLORING THE MECHANISM OF THE ELECTRONIC QUENCHING OF NO (A2Σ+) WITH CO2

Author(s)

Bridgers, Aerial

Contributor(s)

Petit, Andrew S.

Issue Date

2023-06-22

Keyword(s)

Photodissociation and photochemistry

Abstract

As a reactive radical species, NO has the potential to interact with other atmospheric molecules in unique ways. The method of experimental quantification, laser-induced fluorescence (LIF), measures NO along its A²Σ⁺ ← X²Π transition band. The electronic quenching of NO (A²Σ⁺) through interactions with other molecules provides alternate photochemical pathways that compete with fluorescence. Previous experimental studies demonstrated that the room temperature electronic quenching cross section of the NO (A²Σ⁺)+CO₂ system is quite large at 64A˚². Recent experimental work by Paci et al. demonstrated that NO (A²Σ⁺)+CO₂ electronic quenching is accompanied by the formation of vibrationally excited CO₂ in its asymmetric stretching mode. However, the specific photochemical pathways responsible for this have not been identified. In this work, we develop potential energy surfaces (PESs) to identify the photochemical pathways for the electronic quenching of NO (A²Σ⁺) by CO₂. The PESs are calculated at the EOM-EA-CCSD/d-aug-cc-pVTZ//EOM-EA- CCSD/aug-cc-pVDZ level of theory. This method is well-suited for open-shell systems and provides a balanced treatment of valence and Rydberg states. Long-range interactions between the N of NO (A²Σ⁺) and the O of CO₂ are attractive, causing the two molecules to move closer together. As the intermolecular distance decreases, electronic density shifts from the 3sσ orbital of NO (A²Σ⁺) to a 2pπ∗ orbital of CO₂. This phenomenon, known as the harpoon mechanism, causes increased intermolecular attractions, distortion of CO₂ into a bent conformation, and a downhill pathway to a conical intersection. Overall, our work gives new insights into the chemical physics of an atmospherically relevant system that will velocity map imaging experiments.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122346

DOI

https://doi.org/10.15278/isms.2023.6888

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