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Detection of Butadiynyliminomethylium, HC5N+, in the ISM
N. Marcelino, M. Agúndez, B. Tercero, C. Cabezas, C. Bermúdez, J. D. Gallego, P. de Vicente, and J. Cernicharo,
reported on the
Tentative Detection of HC<sub>5</sub>NH<sup>+</sup> in TMC-1
Astron Astrophys. 643, Art. No. L6 (2020).
Two transitions, J“ = 3 and 4 near 35.7 and 44.6 GHz, of a new, unknown molecule were detected 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. Subsequently, two additional transitions, J” = 9 and 10 near 89.2 and 98.1 GHz, were identified in data from an older IRAM 30 m line survey of TMC-1. Laboratory measurements confirmed the identity of the molecule as ethynyloxomethylium.
The abundance ratio of C3O to HC3O+ is ~7, extremely low, whereas astrochemical modeling with protonation of C3O as dominant source of HC3O+ yielded a ratio of ~500 at steady state. The abundance ratio of C3S to HC3S+ should be even lower because of the larger proton affinity of C3S compared to C3O. However, HC3S+ was not detected, and the C3S to HC3S+ ratio was evaluated to be larger than 25, strongly suggesting that protonation of C3O is not an important source of HC3O+ in TMC-1.
Contributor(s): H. S. P. Müller 10, 2020