Laboratory And Astronomical Discovery Of The Cyanovinyl Radical H2CCCN

By Keith Cowing
Status Report
July 19, 2023
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Laboratory And Astronomical Discovery Of The Cyanovinyl Radical H2CCCN
Molecular structure of the H2CCCN radical. — astro-ph.GA

We report the first laboratory and interstellar detection of the alpha-cyano vinyl radical (H2CCCN). This species was produced in the laboratory by an electric discharge of a gas mixture of vinyl cyanide, CH2CHCN, and Ne, and its rotational spectrum was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer operating in the frequency region of 8-40 GHz.

The observed spectrum shows a complex structure due to tunneling splittings between two torsional sublevels of the ground vibronic state, 0+ and 0-, derived from a large-amplitude inversion motion. In addition, the presence of two equivalent hydrogen nuclei makes necessary to discern between ortho- and para-H2CCCN. A least squares analysis reproduces the observed transition frequencies with a standard deviation of ca. 3 kHz. Using the laboratory predictions, this radical is detected in the cold dark cloud TMC-1 using the Yebes 40m telescope and the QUIJOTE line survey.

The 404-303 and 505-404 rotational transitions, composed of several hyperfine components, were observed in the 31.0-50.4 GHz range. Adopting a rotational temperature of 6K we derive a column density of (1.4+/-0.2)e11 cm-2 and (1.1+/-0.2)e11 cm-2 for ortho-H2CCCN and para-H2CCCN, respectively. The reactions C + CH3CN, and perhaps also N + CH2CCH, emerge as the most likely routes to H2CCCN in TMC-1.

C. Cabezas, J. Tang, M. Agúndez, K. Seiki, Y. Sumiyoshi, Y. Ohshima, B. Tercero, N. Marcelino, R. Fuentetaja, P. de Vicente, Y. Endo, J. Cernicharo

Comments: Accepted for publication in A&A Letters on 18/07/2023
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2307.09127 [astro-ph.GA] (or arXiv:2307.09127v1 [astro-ph.GA] for this version)
Submission history
From: Carlos Cabezas
[v1] Tue, 18 Jul 2023 10:17:47 UTC (626 KB)

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