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Highly-Excited State Properties of Cumulenone Chlorides in the Vacuum-Ultraviolet

preprint
submitted on 07.04.2020 and posted on 08.04.2020 by Quynh Nguyen, William Peters, Ryan Fortenberry

Recent observations of chloromethane in interstellar environments suggest that other organohalo- gens, which are known to be critically important in Earth′s atmosphere, may also be of significance beyond our own terrestrial veil. This raises the question of how such molecules behave under extreme conditions such as when exposed to vacuum ultraviolet (VUV) radiation. VUV photons promote molecules to highly excited states that fragment in non-statistical patterns controlled by the initial femtosecond dynamics. A detailed understanding of VUV-driven photochemistry in complex organic molecules that consist of more than one functional group is a particularly challenging task. This quantum chemical analysis reports the electronic states and ionization potentials up to the VUV range (6 - 11 eV) of the chlorine-substituted cumulenone series molecules. The valence and Rydberg properties of lone-pair terminated, π-conjugated systems are explored for their potential resonance with lone pairs from elsewhere in the system. The carbon chain elongation within the family ClHCnO, where n=1-4, influences the electronic excitations, associated wavefunctions, and ionization poten- tials of the molecules. The predicted geometries and ionization potentials are in good agreement with the available experimental photoelectron spectra for formyl chloride and chloroketene, n=1-2. Furthermore, comparison between the regular cumulenone species and the corresponding chlorinated derivatives exhibit similar behaviors especially for n=3, where the allene backbone in propadienone chloride is severely bent. Most notably for the excited states is that the Rydberg character becomes more dominant as the energy increases, with some retaining valence characters.

Funding

Department of Energy Office of Basic Energy Sciences (DE-SC0012628), National Science Foundation Graduate Research Fellowship (DGE-1144083), National Aeronautics and Space Administration (NNX17AH15G), National Science Foundation (OIA- 1757220).

History

Email Address of Submitting Author

qldnguyen@gmail.com

Institution

University of Colorado Boulder

Country

United States

ORCID For Submitting Author

0000-0002-5897-8576

Declaration of Conflict of Interest

The authors have no conflicts to declare.

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