===== On the Detection of Ethynylium in Space =====

A. M. Jacob, K. M. Menten, S. Brünken, A. Belloche, F. Wyrowski, W. G. D. P. Silva, O. Asvany, S. Khan, S. Kabanovic, K. Steenbakkers, G. C. Groenenboom, B. Redlich, and S. Schlemmer\\
reported on the\\
**[[https://doi.org/10.1051/0004-6361/202661924|First Detection of C2H+ in the Interstellar Medium]]**\\
//Astron. Astrophys.// **714**, Art. No. A137 (2026).\\
Ethynylium, with a <sup>3</sup>Π electronic ground state, was detected with the APEX 12 m sub-mm telescope in its lowest Ω = 2 //J// = 3 − 2 transition near 211.5 GHz toward the Orion Bar. The four strong hyperfine transitions, Δ//F// = +1, two each in the //f// and //e// Λ-doublets, were detected with good signal-to-noise ratio (S/N). The S/N was too low to detect the two weaker Δ//F// = 0 transitions. Ethynylium is about a factor of 15000 less abundant that the neutral C<sub>2</sub>H and about a factor of ~40 less than //l//-C<sub>3</sub>H.\\
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Contributor(s): H. S. P. Müller; 10, 2026

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