2014ApJ...796..139F

The anion chemistry of the interstellar medium (ISM) has almost exclusively been limited to linear hydrocarbons and cyanocarbons. Of the hydrocarbons, only the even n C_nH^– chains have been detected in the ISM, and lines hypothesized to originate with b-C₃H^– have been conclusively linked to the corresponding cation, as originally claimed. However, no reason has yet been provided as to why other anions cannot form, and the cyclic form of C₃H^– is actually the lowest-energy isomer on the anion's potential energy surface. As such, this work provides the necessary rovibrational reference data for the potential detection of this anion in the ISM or related laboratory experiments. Improvements over previously calculated rovibrational spectroscopic constants are contained herein along with graphical depictions of the pure rotational spectra at 100 K, 40 K, 20 K, and 2.7 K.