High-resolution rotational spectroscopy of the carbon chain anions C3N-, C4H-, and C4D(-).

The rotational spectra of C(3)N(-), C(4)H(-), and C(4)D(-) have been measured at high-spectral resolution by Fourier transform microwave spectroscopy. For both C(3)N(-) and C(4)D(-), hyperfine structure in the lowest-J transitions has been resolved and measured to better than 0.1 ppm. The quadrupole coupling constants eQq for both anions are close to those of the neutral counterparts C(3)N and C(4)D, and that of C(3)N(-) is in good agreement with theoretical calculations. Several properties of these anions, including their linewidths, drift velocities, and abundances, are systematically compared to similar-sized neutral molecules. The production of C(4)H(-) with different hydrocarbon precursor and buffer gases is also discussed.