Negative ions formed in N2/CH4/Ar discharge – A simulation of Titan’s atmosphere chemistry

The formation of negative ions produced in a negative point-to-plane corona discharge fed by a Ar/N2/CH4 gas mixture has been studied using mass spectrometry. The measurements were carried out in flowing regime at ambient temperature and a reduced pressure of 460 mbar. The CN− anion has been found to be the most dominant negative ion in the discharge and is believed to be the precursor of heavier negative ions such as C3N − and C5N−. The most likely pathway for the formation of such molecular anions is H-loss dissociative electron attachment to HCN, H3CN and H5CN formed in the discharge. These same anions have been detected in Titan’s atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan’s atmosphere and hence assist in the interpretation of results from the Cassini Huygens space mission. PACS. 52.50.Dg Plasma sources – 52.80.Hc Glow; corona – 96.50.Dj Interplanetary dust and gas