Frequency variation of the mean energy of r.f. electron swarms

Starting from the general momentum and energy balance equations for charged particle swarms in a gas, as furnished by momentum-transfer theory, the authors obtain expressions for mean velocity and mean energy of an electron swarm in an r.f. electric field under spatially uniform conditions, in the frequency range ω τe > 1, where τe is the energy collisional relaxation time. If τe is a decreasing function of energy, it is shown that the cycle-averaged mean energy reaches a maximum at a certain frequency. Physical arguments are provided to support this result and the prediction is verified for a constant elastic cross section model by direct numerical solution of Boltzmann's equation. 21 refs., 2 figs