| Issue |
A&A
Volume 671, March 2023
|
|
|---|---|---|
| Article Number | A95 | |
| Number of page(s) | 11 | |
| Section | Interstellar and circumstellar matter | |
| DOI | https://doi.org/10.1051/0004-6361/202245643 | |
| Published online | 13 March 2023 | |
Gas-phase formation and spectroscopic characterization of the disubstituted cyclopropenylidenes c-C3(C2H)2, c-C3(CN)2, and c-C3(C2H)(CN)★
Department of Chemistry and Biochemistry, University of Mississippi, University,
Mississippi
38677-1848, USA
e-mail: r410@olemiss.edu@
Received:
7
December
2022
Accepted:
17
January
2023
Aims. The detection of c-C3HC2H and possible future detection of c-C3HCN provide new molecules for reaction chemistry in the dense interstellar medium (ISM) where R-C2H and R-CN species are prevalent. Determination of chemically viable c-C3HC2H and c-C3HCN derivatives and their prominent spectral features can accelerate potential astrophysical detection of this chemical family. This work characterizes three such derivatives: c-C3(C2H)2, c-C3(CN)2, and c-C3(C2H)(CN).
Methods. Interstellar reaction pathways of small carbonaceous species are well replicated through quantum chemical means. Highly accurate cc-pVXZ-F12/CCSD(T)-F12 (X = D,T) calculations generate the energetics of chemical formation pathways as well as the basis for quartic force field and second-order vibrational perturbation theory rovibrational analysis of the vibrational frequencies and rotational constants of the molecules under study.
Results. The formation of c-C3(C2H)2 is as thermodynamically and, likely, as stepwise favorable as the formation of c-C3HC2H, rendering its detectability to be mostly dependent on the concentrations of the reactants. Both c-C3(C2H)2 and c-C3(C2H)(CN) will be detectable through radioastronomical observation with large dipole moments of 2.84 D and 4.26 D, respectively, while c-C3(CN)2 has an exceedingly small and likely unobservable dipole moment of 0.08 D. The most intense frequency for c-C3(C2H)2 is v2 at 3316.9 cm–1 (3.01 μm), with an intensity of 140 km mol–1. The mixed-substituent molecule c-C3(C2H)(CN) has one frequency with a large intensity, v1, at 3321.0 cm–1 (3.01 μm), with an intensity of 82 km mol–1. The molecule c-C3(CN)2 lacks intense vibrational frequencies within the range that current instrumentation can readily observe.
Conclusions. Both c-C3(C2H)2 and c-C3(C2H)(CN) are viable candidates for astrophysical observation, with favorable reaction profiles and spectral data produced herein, but c-C3(CN)2 will not be directly observable through any currently available remote sensing means, even if it forms in large abundances.
Key words: astrochemistry / ISM: molecules / infrared: ISM / molecular processes
Additional data obtained from spectroscopic analysis alongside structural information for all molecules can be found at https://egrove.olemiss.edu/chem_facpubs/33
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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