CN And CCH Derivatives Of Ethylene And Ethane: Confirmation Of The Detection Of CH3CH2CCH In TMC-1

By Keith Cowing
Status Report
April 12, 2024
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CN And CCH Derivatives Of Ethylene And Ethane: Confirmation Of The Detection Of CH3CH2CCH In TMC-1
Observed lines of CH3CH2CCH in TMC-1. The line parameters are given in Table A.1. The abscissa corresponds to the rest frequency assuming a velocity for the source of 5.83 km s−1 . The ordinate is the antenna temperature corrected for atmospheric and telescope losses in mK. Quantum numbers are indicated in the top right corner of each panel. The red line corresponds to the synthetic spectrum derived from the LTE model described in Sect. 3.1. Blanked channels correspond to negative features produced in the folding of the frequency-switching data. For some lines, we found a frequency shift of up to ±40 kHz with respect to the predictions (see Sect. 3.1). This is indicated in magenta in the corresponding panels. — astro-ph.GA

We present a study of CH3CH2CCH, CH3CH2CN, CH2CHCCH, and CH2CHCN in TMC-1 using the QUIJOTE1 line survey. We confirm the presence of CH3CH2CCH in TMC-1, which was previously reported as tentative by our group.

From a detailed study of the ethynyl and cyanide derivatives of CH2CH2 and CH3CH3 in TMC-1, we found that the CH2CHCCH/CH2CHCN and CH3CH2CCH/CH3CH2CN abundance ratios are 1.5±0.1 and 4.8±0.5, respectively. The derived CH2CHCCH/CH3CH2CCH abundance ratio is 15.3±0.8, and that of CH2CHCN over CH3CH2CN is 48±5.

All the single substituted isotopologs of vinyl cyanide have been detected, and we found that the first and second carbon substitutions in CH2CHCN provide a 12C/13C ratio in line with that found for other three-carbon bearing species such as HCCNC and HNCCC.

However, the third 13C isotopolog, CH2CH13CN, presents an increase in its abundance similar to that found for HCCCN. Finally, we observed eight b-type transitions of CH2CHCN, and we find that their intensity cannot be fitted adopting the dipole moment μb derived previously. These transitions involve the same rotational levels as those of the a-type transitions.

From their intensity, we obtain μb=0.80±0.03\,D, which is found to be in between earlier values derived in the laboratory using intensity measurements or the Stark effect. Our chemical model indicates that the abundances of CH3CH2CCH, CH3CH2CN, CH2CHCCH, and CH2CHCN observed in TMC-1 can be explained in terms of gas-phase reactions.

J. Cernicharo, B. Tercero, M. Agúndez, C. Cabezas, R. Fuentetaja, N. Marcelino, P. de Vicente

Comments: Accepted as a Letter in Astronomy & Astrophysics on March 8th 2024
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2404.07585 [astro-ph.GA] (or arXiv:2404.07585v1 [astro-ph.GA] for this version)
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Submission history
From: Carlos Cabezas
[v1] Thu, 11 Apr 2024 09:17:23 UTC (460 KB)
Astrobiology, Astrochemistry,

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻