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

Three molecular anions, CN(-), C(2)H(-), and C(4)H(-), 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 C(2)N(2) or C(2)H(2) of 2 mTorr and Ar or Ne buffer of 15 mTorr was used for the production of CN(-) or C(2)H(-) and C(4)H(-). The number densities of the anions in the cell were estimated to be approximately 1x10(9), approximately 3x10(7), and approximately 3x10(6) cm(-3) for CN(-), C(2)H(-), and C(4)H(-), respectively.