Hunting the relatives of benzonitrile: Rotational spectroscopy of dicyanobenzenes

Abstract

<jats:p><jats:italic>Context.</jats:italic> The recent interstellar detections of –CN containing aromatic species, namely benzonitrile, 1-cyanonaphthalene, and 2-cyanonaphthalene, bring renewed interest in related molecules that could participate in similar reaction networks.</jats:p> <jats:p><jats:italic>Aims.</jats:italic> To enable new interstellar searches for benzonitrile derivatives, the pure rotational spectra of several related species need to be investigated in the laboratory.</jats:p> <jats:p><jats:italic>Methods.</jats:italic> We have recorded the pure rotational spectra of ortho- and meta-dicyanobenzene in the centimetre and millimetre-wave domains. Assignments were supported by high-level quantum chemical calculations. Using Markov chain Monte Carlo simulations, we also searched for evidence of these molecules towards TMC-1 using the GOTHAM survey.</jats:p> <jats:p><jats:italic>Results.</jats:italic> Accurate spectroscopic parameters are derived from the analysis of the experimental spectra, allowing for reliable predictions at temperatures of interest (i.e. 10–300 K) for astronomical searches. Our searches in TMC-1 for both ortho- and meta-isomers provide upper limits for the abundances of the species.</jats:p>