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.
Subject
Space and Planetary Science,Astronomy and Astrophysics
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