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Douglas-Walker, Thomas E., Ashworth, Eleanor K., Stockett, Mark H., Daly, Francis C., Chambrier, Isabelle, Esposito, Vincent J., Gerlach, Marius, Zheng, Angel, Palotás, Julianna, Cammidge, Andrew N. 
ORCID: https://orcid.org/0000-0001-7912-4310, Campbell, Ewen K., Brünken, Sandra and Bull, James N. ORCID: https://orcid.org/0000-0003-0953-1716
(2025)
Vibrational and electronic spectroscopy of 2-cyanoindene cations.
ACS Earth and Space Chemistry, 9 (1).
134–145.
ISSN 2472-3452
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Abstract
2-Cyanoindene is one of the few specific aromatic or polycyclic aromatic hydrocarbon (PAH) molecules positively identified in Taurus molecular cloud-1 (TMC-1), a cold, dense molecular cloud that is considered the nearest star-forming region to Earth. We report cryogenic mid-infrared (550–3200 cm–1) and visible (16,500–20,000 cm–1, over the D2 ← D0 electronic transition) spectra of 2-cyanoindene radical cations (2CNI+), measured using messenger tagging (He and Ne) photodissociation spectroscopy. The infrared spectra reveal the prominence of anharmonic couplings, particularly over the fingerprint region. There is a strong CN-stretching mode at 2177 ± 1 cm–1 (4.593 μm), which may contribute to a broad plateau of CN-stretching modes across astronomical aromatic infrared band spectra. However, the activity of this mode is suppressed in the dehydrogenated (closed shell) cation, [2CNI-H]+. The IR spectral frequencies are modeled by anharmonic calculations at the B3LYP/N07D level of theory that include resonance polyad matrices, demonstrating that the CN-stretch mode remains challenging to describe with theory. The D2 ← D0 electronic transition of 2CNI+, which is origin dominated, occurs at 16,549 ± 5 cm–1 in vacuum (6041.8 Å in air). There are no correspondences with reported diffuse interstellar bands.
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| Additional Information: | Acknowledgments: This work was funded by an EPSRC New Investigator Award (EP/W018691 to J.N.B.) and standard grant (EP/W03753X to E.K.C.), the Royal Society (RGF/EA/181035, RF/ERE/210238, URF/R1/180162, and URF/R1/231018 to E.K.C.), and the Olle Engkvist Foundation (200-575 to M.H.S.). We gratefully acknowledge the support of the Radboud University and of the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) for providing the required beam time at the FELIX laboratory and the skillful assistance of the FELIX staff. We thank the Cologne Laboratory Astrophysics group for providing the FELion ion trap instrument for the current experiments and the Cologne Center for Terahertz Spectroscopy funded by the Deutsche Forschungsgemeinschaft (DFG, grant SCHL 341/15-1) for supporting its operation. This publication is based upon work from COST Action CA21126 - Carbon molecular nanostructures in space (NanoSpace), supported by COST (European Cooperation in Science and Technology). E.K.A. thanks the University of East Anglia for a doctoral scholarship and the NanoSpace COST Action network for funding a short term scientific mission to visit FELIX. Electronic structure calculations were, in part, carried out on the high performance computing cluster supported by the Research and Specialist Computing Support service at the University of East Anglia. V.J.E. acknowledges an appointment to the NASA Postdoctoral Program at NASA Ames Research Center, administered by the Oak Ridge Associated Universities through a contract with NASA and support from the Internal Scientist Funding Model (ISFM) Laboratory Astrophysics Directed Work Package at NASA Ames. Computer time from the Pleiades and Aiken clusters of the NASA Advanced Supercomputer (NAS) is gratefully acknowledged. M.G. thanks the DFG for funding via the Walter Benjamin-Programm. |
| Faculty \ School: | Faculty of Science > School of Chemistry, Pharmacy and Pharmacology |
| UEA Research Groups: | Faculty of Science > Research Groups > Centre for Photonics and Quantum Science Faculty of Science > Research Groups > Chemistry of Materials and Catalysis Faculty of Science > Research Groups > Chemistry of Light and Energy |
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| Depositing User: | LivePure Connector |
| Date Deposited: | 18 Dec 2024 01:39 |
| Last Modified: | 18 Jan 2025 01:07 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/98017 |
| DOI: | 10.1021/acsearthspacechem.4c00270 |
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