Extended negative glow and hollow anode discharges for submillimeter-wave observation of CN-, C2H-, and C4H-

Three molecular anions, CN-, C2H-, and C4H-, have been detected in an extended negative glow discharge and a hollow anode discharge in the submillimeter-wave region. These electrical discharges have been unexpectedly found to be reasonable anion sources. The measurements have been extended up to 830 GHz, and the molecular constants have been improved significantly compared with those determined by microwave and millimeter-wave spectroscopy. The parent gas mixture of C2N2 or C2H2 of 2 mTorr and Ar or Ne buffer of 15 mTorr was used for the production of CN- or C2H- and C4H-. The number densities of the anions in the cell were estimated to be similar to 1x10(9), similar to 3x10(7), and similar to 3x10(6) cm(-3) for CN-, C2H-, and C4H-, respectively.