molecules:ism:hcxn-plus [CDMS classic documentation]

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===== On HCxN+ in the ISM =====

 J. Cernicharo, C. Cabezas, M. Agúndez, Y. Endo, B. Tercero, N. Marcelino and P. de Vicente\\
reported on the\\
**[[https://doi.org/10.1051/0004-6361/202450801|QUIJOTE discovery of the cation radicals HC5N+ and HC7N+]]**\\
//Astron. Astrophys.// **686**, Art. No. L15 (2024).\\
HC<sub>5</sub>N<sup>+</sup> and HC<sub>7</sub>N<sup>+</sup> were identified through 7 and 8 unblended or slightly blended transitions in their <sup>2</sup>Π<sub>3/2</sub> lower spin ladder, respectively, with 23/2 ≤ //J// ≤ 37/2 in the first case and 53/2 ≤ //J// ≤ 69/2 in the latter. The identifications were made 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 50.3 GHz. //T//<sub>rot</sub> = 8.5 ± 0.5 K was derived for HC<sub>5</sub>N<sup>+</sup>, while //T//<sub>rot</sub> = 7.8 ± 0.1 K was derived for HC<sub>7</sub>N<sup>+</sup>. The abundance ratios present a consistent and interesting picture. The HC<sub>5</sub>N<sup>+</sup> / HC<sub>7</sub>N<sup>+</sup> ratio is ~4.2; the HC<sub>5</sub>N<sup>+</sup> / HC<sub>5</sub>N, HC<sub>5</sub>N<sup>+</sup> / C<sub>5</sub>N<sup>−</sup>, and HC<sub>5</sub>N<sup>+</sup> / C<sub>5</sub>N<sup>−</sup> ratios are about 670, 4.8, and 1.2, respectively, while the HC<sub>7</sub>N<sup>+</sup> / HC<sub>7</sub>N and HC<sub>7</sub>N<sup>+</sup> / C<sub>7</sub>N<sup>−</sup> ratios are about 1000 and 2.2, respectively.\\
\\

Shortly thereafter,\\
C. Cabezas, M. Agúndez, Y. Endo, B. Tercero, N. Marcelino, P. de Vicente, and J. Cernicharo\\
published on the\\
**[[https://doi.org/10.1051/0004-6361/202451081|Discovery of the interstellar cyanoacetylene radical cation HC3N+]]**\\
//Astron. Astrophys.// **687**, Art. No. L22 (2024).\\
The QUIJOTE survey of TMC-1 was employed once more to identify the six strong hyperfine structure components of the //J// = 7/2 − 5/2 near 31.63 GHz and 9/2 − 7/2 near 40.66 GHz in its <sup>2</sup>Π<sub>3/2</sub> lower spin ladder with good signal-to-noise ratio. The HFS components where not or only slightly blended with the exception of one in the upper transition. Supporting, but less favorable results were presented for the 11/2 − 9/2 transition near 49.965 GHz. The rotational temperature was estimated to be 4.5 K. The HC<sub>3</sub>N to HC<sub>3</sub>N<sup>+</sup> ratio is about 3200; the C<sub>3</sub>N to HC<sub>3</sub>N<sup>+</sup> ratio about 300; the HC<sub>3</sub>N<sup>+</sup> to HC<sub>5</sub>N<sup>+</sup> ratio is about 0.6.\\
\\

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Contributor(s): H. S. P. Müller; 06, 2024; 07, 2024

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