Volume 643, November 2020
|Number of page(s)||9|
|Section||Letters to the Editor|
|Published online||27 October 2020|
Letter to the Editor
Tentative detection of HC5NH+ in TMC-1⋆
Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain
2 Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
3 Observatorio Astronómico Nacional (IGN), C/ Alfonso XII, 3, 28014 Madrid, Spain
Accepted: 4 September 2020
Using the Yebes 40m radio telescope, we report the detection of a series of seven lines harmonically related with a rotational constant B0 = 1295.81581 ± 0.00026MHz and a distortion constant D0 = 27.3 ± 0.5Hz towards the cold dense cloud TMC-1. Ab initio calculations indicate that the best possible candidates are the cations HC5NH+ and NC4NH+. From a comparison between calculated and observed rotational constants and other arguments based on proton affinities and dipole moments, we conclude that the best candidate for a carrier of the observed lines is the protonated cyanodiacetylene cation, HC5NH+. The HC5N/HC5NH+ ratio derived in TMC-1 is 240, which is very similar to the HC3N/HC3NH+ ratio. Results are discussed in the framework of a chemical model for protonated molecules in cold dense clouds.
Key words: astrochemistry / ISM: molecules / ISM: individual objects: TMC-1 / line: identification / molecular data
© ESO 2020
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