Electron rate coefficients in gases under non-uniform field and electron density conditions

The theory of perturbation is used to describe electron rate coefficients in gases under non-uniform field and electron-density conditions when the deviation from spatial uniformity is small. It is shown that the space-dependent rate coefficients can be represented as a sum of the local values and the product of new rate coefficients dependent on the local field and the gradients of the field and of the electron density. By solving the Boltzmann equation in a two-term approximation, the new rate coefficients are calculated for N-2, CO2, and Ar. The results of our calculations are compared with experimental data on the relative excitation rates in a steady-state Townsend discharge in a CO2:N-2:He:CO mixture and with results of previous Monte Carlo simulations of the electron swarm behaviour in non-uniform fields.