Eur. Phys. J. D (2014) 68: 216
https://doi.org/10.1140/epjd/e2014-40836-9

Regular Article

Experimental simulation of negative ion chemistry in Martian atmosphere using ion mobility spectrometry-mass spectrometry^*

¹ Department of Experimental Physics, Comenius University Bratislava, Mlynská dolina F2, 84248 Bratislava, Slovakia
² Department of Physics and Astronomy, The Open University, Walton Hall, MK7 6 AA Milton Keynes, UK

^a e-mail: matejcik@fmph.uniba.sk

Received: 28 December 2013
Received in final form: 18 April 2014
Published online: 7 August 2014

Abstract

We have studied the formation of negative ions in a negative Corona Discharge (CD) fed by CO₂/N₂ mixtures (with 0, 2, 4, 6, 8, 10% N₂) using the technique of ion mobility spectrometry-orthogonal acceleration time of flight mass spectrometry (IMS-oaTOF). The composition of the negative ions was found to be dependent on the initial gas composition, the gas flow regime, the concentrations of neutral reactive species formed in the discharge and the trace amounts on water in the gases were found to play an important role in the negative ions formation. In a pure CO₂ discharge operating under standard gas flow conditions of IMS (associated with strong interaction of ions with neutral reactive species formed in discharge) the ions CO₃⁻ (H₂O) and CO₄⁻(H₂O) dominated the measured negative ion spectrum while in CO₂/N₂ mixtures NO₃⁻(H₂O)_n, NO₃⁻(HNO₃) (n = 0, 1) ions prevailed. In the case of reverse gas flow regime (low interaction of ions with neutral reactive species formed in discharge), the negative ions detected were O₂⁻(H₂O)_n, and O₂⁻.CO₂(H₂O)_n both in pure CO₂ and N₂/CO₂ mixtures. The spectra of negative ions recorded for a gas mixture containing 4% N₂ in CO₂ were compared with theoretical predictions of negative ion composition in the lower atmosphere of Mars.