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

¹ Department of Experimental Physics, Comenius University, Mlynska dolina F-2, 842 48 Bratislava, Slovakia
² Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
³ Plasma & Surface Analysis Division, Hiden Analytical Ltd., 420 Europa Boulevard, Warrington, WA5 7UN, UK

Corresponding author: horeszka@gmail.com

Received: 30 June 2009
Revised: 1 September 2009
Accepted: 12 October 2009
Published online: 26 November 2009

Abstract

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.