Momentum transfer theory of nonconservative charged particle transport in mixtures of gases: General equations and negative differential conductivity

In this paper we develop general equations for the momentum transfer theory (MTT) for swarms of particles in mixtures of gases including the effect of nonconservative (reactive) collisions. MTT equations for mean energy, drift velocity, diffusion tensor components, and rate coefficients are derived for different degrees of approximation including the hydrodynamic limit and small swarm to gas particle mass ratio. Specific formulas were developed for the criteria for negative differential conductivity (NDC) in mixtures of gases with elastic collisions only and for a single gas with reactions. The criteria and the numerical calculations are in excellent agreement, showing that NDC can be induced by light atomic constituents in purely elastic collisions and also by ionization and attachment.