Submillimeter-wave spectrum of C3N- in the extended negative glow and hollow-anode discharges

The pure rotational transitions of C3N- have been observed in the frequency range of 359-504 GHz. An extended negative glow discharge and a hollow-anode discharge in a gas mixture of C2N2 (0.3-2 mTorr) and C2H2 (2-3 mTorr) diluted in Ar or Ne buffer gas of about 15 mTorr pressure prove to be an excellent source of the negative ion. Throughout the experiments, the cell was cooled down to about −45 °C. In the present study, we have determined the accurate molecular constants including a higher order centrifugal distortion constant H. The number density of C3N- in the discharge cell is estimated to be about 3.6×106 cm−3. The chemical processes related to this anion and other neutral species are briefly discussed.