Collision cross sections and swarm coefficients of water vapour ion clusters (H₂O) _n H⁺ with n = 1, 2 and 3 in N₂, O₂ and air

Abstract.

The ion swarm transport coefficients such as reduced mobility, diffusion coefficients and reaction rates of three water vapour ion clusters (H₂O) _n H⁺ (with n = 1, 2 and 3) in N₂ and O₂ have been determined from a Monte Carlo simulation using calculated and measured elastic and inelastic collision cross sections. The elastic momentum transfer cross sections have been determined from a semi-classical JWKB approximation based on a rigid core interaction potential model. The inelastic cross sections have been deduced from the measured ones in the case of similar ion cluster. Then, the cross sections sets are fitted using either the measured reduced mobility at low electric field in the case of (H₂O) _n H⁺ in N₂ or the zero-field mobility calculated from the Satoh's relation and the measured ones in N₂. From the sets of elastic and inelastic collision cross sections thus obtained in pure N₂ and O₂, the ion transport and reaction coefficients for (H₂O) _n H⁺ are then calculated in dry air and also extended over a wide range of reduced electric field in N₂ and O₂. These ion data are very useful for modelling and simulation of non-equilibrium electrical discharges more particularly in humid gases at atmospheric pressure.