Discovery of HC3O+ in space: The chemistry of O-bearing species in TMC-1

TL;DR

This paper reports the first detection of HC3O+ in space, combining radio telescope observations, laboratory synthesis, and theoretical calculations to understand the chemistry of oxygen-bearing molecules in TMC-1.

Contribution

It provides the first identification of HC3O+ in space, supported by observational, experimental, and computational evidence, advancing knowledge of interstellar oxygen chemistry.

Findings

HC3O+ detected in TMC-1 with specific rotational constants

Laboratory production and observation of HC3O+ rotational transitions

Derived abundance ratio N(C3O)/N(HC3O+) = 7

Abstract

Using the Yebes 40m and IRAM 30m radio telescopes, we detected a series of harmonically related lines with a rotational constant B0=4460.590 +/- 0.001 MHz and a distortion constant D0=0.511 +/- 0.005 kHz towards the cold dense core TMC-1. High-level-of-theory ab initio calculations indicate that the best possible candidate is protonated tricarbon monoxide, HC3O+. We have succeeded in producing this species in the laboratory and observed its J = 2-1 and 3-2 rotational transitions. Hence, we report the discovery of HC3O+ in space based on our observations, theoretical calculations, and laboratory experiments. We derive an abundance ratio N(C3O)/N(HC3O+) = 7. The high abundance of the protonated form of C3O is due to the high proton affinity of the neutral species. The chemistry of O-bearing species is modelled, and predictions are compared to the derived abundances from our data for the most prominent O-bearing species in TMC-1.