Boltzmann equation analysis of electron swarm behaviour in methane

The electron swarm behaviour in methane is studied for E/p 0 from 0.2 to 200 V cm -1 Torr -1 by a Boltzmann equation method. The alteration of cross sections from the literature is avoided as much as possible in the analysis. The swarm parameters are calculated for the pulsed Townsend, steady-state Townsend and time-of-flight experiments. Moreover, the accuracy of the two-term approximation is checked by a Monte Carlo simulation. The values of the ionisation coefficient, electron drift velocity and characteristic energy calculated are found to agree well with the experimental ones if these values are properly interpreted. This result suggests that the set of electron collision cross sections tailored in the present analysis is an appropriate one. The electron energy distribution, and the excitation frequencies for vibration and dissociation are also calculated and discussed.