Discovery of H<sub>2</sub>CCCH<sup>+</sup> in TMC-1
Weslley G. D. P. Silva, J. Cernicharo, Stephan Śchlemmer, N. Marcelino, Jean‐Christophe Loison, M. Agúndez, Divita Gupta, Valentine Wakelam, Sven Thorwirth, C. Cabezas, B. Tercero, José Luis Doménech, R. Fuentetaja, W.-J. Kim, P. de Vicente, Oskar Asvany
Abstract
Based on a novel laboratory method, 14 millimeter-wave lines of the molecular ion H 2 CCCH + have been measured in high resolution, and the spectroscopic constants of this asymmetric rotor determined with high accuracy. Using the Yebes 40 m and IRAM 30 m radio telescopes, we detected four lines of H 2 CCCH + toward the cold dense core TMC-1. With a dipole moment of about 0.55 D obtained from high-level ab initio calculations, we derive a column density of 5.4±1×10 11 cm −2 and 1.6±0.5×10 11 cm −2 for the ortho and para species, respectively, and an abundance ratio N(H 2 CCC)/N(H 2 CCCH + ) = 2.8±0.7. The chemistry of H 2 CCCH + is modeled using the most recent chemical network for the reactions involving the formation of H 2 CCCH + . We find a reasonable agreement between model predictions and observations, and new insights into the chemistry of C 3 -bearing species in TMC-1 were obtained.