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arXiv · 2201.02434

Discovery of C5H+ and detection of C3H+ in TMC-1 with the QUIJOTE line survey

J. Cernicharo·M. Agundez·C. Cabezas·R. Fuentetaja·B. Tercero·N. Marcelino·Y. Endo·J. R. Pardo·P. de Vicente
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Abstract

We report the discovery of the C5H+ cation toward TMC-1 with the QUIJOTE line survey. Four lines from J=7-6 up to J=10-9 have been identified in perfect harmonic frequency relation that can be fit with B=2411.94397 +/-0.00055 MHz and D=138+/-3 Hz. The standard deviation of the fit is 4.4 kHz. After discarding potential candidates, C5H- among them, we conclude that the carrier is C5H+, for which accurate ab initio calculations provide B=2410.3 MHz. We also report for the first time in a cold starless core the detection of the C3H+ cation. The column densities we derive for C5H+ and C3H+ are (8.8+/-0.5)e10 cm-2 and (2.4+/-0.2)e10 cm-2, respectively. Hence, the C5H+/C3H+ abundance ratio is 3.7+/-0.5. The fact that C5H+ is more abundant than C3H+ is well explained by dedicated chemical models and is due to the slow reactivity of C5H+ with H2, while C3H+ reacts with H2.

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J. Cernicharo, M. Agundez, C. Cabezas, R. Fuentetaja, B. Tercero, N. Marcelino, Y. Endo, J. R. Pardo, P. de Vicente. 2022-01-07. Discovery of C5H+ and detection of C3H+ in TMC-1 with the QUIJOTE line survey. https://doi.org/10.1051/0004-6361/202142992

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