===== On the Detection of Cyanopropargyl in the ISM =====

C. Cabezas, M. Agúndez, N. Marcelino, B. Tercero, J. R. Pardo, P. de Vicente, and J. Cernicharo\\
reported on the\\
**[[https://doi.org/10.1051/0004-6361/202142156|Discovery of Interstellar 3-Cyanopropargyl Radical, CH<sub>2</sub>CCCN]]**\\
//Astron. Astrophys.// **654**, Art. No. L9 (2021).\\
//ortho//-CH<sub>2</sub>C<sub>3</sub>N was identified through three //a//-type transitions with //J// = 8 − 7 to 10 − 9 and //K<sub>a</sub>// = 0 in the course of a molecular line survey of the prototypical cold dark molecular cloud TMC-1 carried out with the Yebes 40 m radio telescope between 31.0 and 50.4 GHz. These transitions displayed partially resolved fine and hyperfine structure splitting; few components were blended by lines of other species. Also observed were four transitions of //para//-CH<sub>2</sub>C<sub>3</sub>N with //J// = 8 − 7 or 9 − 8 and //K<sub>a</sub>// = 1, which displayed well resolved fine structure splitting; some of these lines were also blended. A value of //T//<sub>rot</sub> = 7 ± 1 K was derived. The column density of CH<sub>2</sub>C<sub>3</sub>N is about a factor of 100 lower than that of CH<sub>2</sub>CN. And while CH<sub>2</sub>C<sub>3</sub>N is roughly a factor of 10 less abundant than CH<sub>3</sub>C<sub>3</sub>N, CH<sub>2</sub>CN is **more abundant** than CH<sub>3</sub>CN by a factor of about 3.\\
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More recently,\\
C. Cabezas, M. Agúndez, N. Marcelino, C. H. Chang, R. Fuentetaja, B. Tercero, M. Nakajima, Y. Endo, P. de Vicente, and J. Cernicharo\\
announced the\\
**[[https://doi.org/10.1051/0004-6361/202453419|Identification of the Interstellar 1-Cyanopropargyl Radical (HCCCHCN) in TMC-1]]**\\
//Astron. Astrophys.// **693**, Art. No. L14 (2025).\\
Eight //a//-type transitions with 5 ≤ //J// ≤ 8 and //K<sub>a</sub>// ≤ 1 were covered with complex fine and hyperfine structure splitting. Many features are close to the noise limit or blended, but sufficiently many features are clear enough and modeled well enough to view the detection as secure. A value of //T//<sub>rot</sub> = 7 ± 1 K was derived for this isomer as well. The abundance of 1-cyanopropargyl is slightly higher than that of 3-cyanopropargyl by a factor of about 1.4.\\
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Contributor(s): H. S. P. Müller; 11, 2021; 01, 2025

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