Hunting the relatives of benzonitrile: Rotational spectroscopy of dicyanobenzenes

Context. 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.
Aims: To enable new interstellar searches for benzonitrile derivatives, the pure rotational spectra of several related species need to be investigated in the laboratory.
Methods: 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.
Results: 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.

Data (FITS files) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/652/A163