Basic data of polyatomic ion-molecule systems for flue gas discharge modelling

Abstract

In the presence of an external electric field, ion transport coefficients (ion mobility and diffusion coefficients) are closely related to the ion-neutral interaction potential. A new generalized potential model, coupled to an optimized Monte Carlo technique, has been developed for the determination of the transport coefficients of polyatomic ions in weakly ionized gases. This corresponds to the polyatomic ion-molecule systems which can affect the electrical behaviour of the flue gas discharges used for the non-thermal plasma reactor for pollution control. The ion-molecule interaction has been described by a rigid core potential model which is adapted for both polar and non-polar systems and also symmetric and asymmetric systems. Momentum transfer cross sections are then determined using a semi-classical approach. The corresponding sets of cross sections including the dominant processes in our intermediate ion energy range (elastic and mainly charge transfer in certain cases) are used in the Monte Carlo code to calculate the ion transport coefficients over a wide range of reduced electric field E/N. These ion transport data fit quite well the drift tube measurements available in the literature for the CO₂⁺/CO₂ system, and also for certain weakly polar cases. The case of the H₂O⁺/H₂O system is then considered thus giving in this highly polar system the ion swarm data for the first time in the literature. Finally, we have considered with quite good reliability some asymmetric systems such as CO₂⁺/N₂ and N₂⁺/CO₂ whose ion data are also needed for flue gas discharge modelling.