Discovery of a new molecular ion, HC7NH+, in TMC-1
Abstract
We report the detection of the protonated form of HC7N in TMC-1. The discovery of the cation HC7NH+ was carried out via the observation of nine harmonically related lines in the Q-band using the Yebes 40 m radiotelescope. The observed frequencies allowed us to obtain the rotational constants B0 = 553.938802 (160) MHz and D0 = 3.6292 (705) Hz. The identification of HC7NH+ is further supported by accurate ab initio calculations. We derived a column density of (5.5 ± 0.7) × 1010 cm−2, which constitutes another piece of evidence for the identification of the carrier. In addition, we revised the HC7N column density and we derived a new value of (2.1 ± 0.2) × 1013 cm−2. Hence, the abundance ratio HC7N/HC7NH+ is ∼380, while those for HC3N/HC3NH+ and HC5N/HC5NH+ are ∼230 and ∼240, respectively. Here, we discuss these results within the framework of a chemical model for protonated molecules in cold dense clouds.
Based on observations carried out with the Yebes 40 m telescope (projects 19A003, 20A014, 20D023, and 21A011). The 40 m radiotelescope at Yebes Observatory is operated by the Spanish Geographic Institute (IGN, Ministerio de Transportes, Movilidad y Agenda Urbana).- Publication:
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Astronomy and Astrophysics
- Pub Date:
- March 2022
- DOI:
- 10.1051/0004-6361/202142972
- arXiv:
- arXiv:2203.05617
- Bibcode:
- 2022A&A...659L...8C
- Keywords:
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- astrochemistry;
- ISM: molecules;
- ISM: individual objects: TMC-1;
- line: identification;
- molecular data;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted as Letter to the Editor in Astronomy &