Electron swarm motion has been simulated by using a Monte Carlo technique and swarm parameters have been evaluated for electrons in both hydrogen and carbon monoxide gases for a wide range of E/N varying from 30 to 3000 Td. Comparison has been made with the experimental results for the ionization coefficient, the drift velocity and both the radial and longitudinal diffusion coefficients. A set of electron/molecule collision cross-sections has been assembled for each gas which gave a good fit between the simulated and experimental values over the entire E/N range.

Electron drift velocities have been measured for swarms in caesium vapour by using a heat-pipe drift tube. The heat-pipe was used to both generate and to contain the caesium vapour. The electron transit times between the cathode and anode were measured for a variable gap separation by the induced charge method. Electron drift velocities were obtained as a function of E/N (ratio of electric field to vapour number density) for the range of 4

Experimental values have been given for both the drift velocity and the ratio of longitudinal diffusion coefficient to mobility for electrons in helium (1.4

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The relationship between the theoretical (v) and experimental (vexp) values of the electron drift velocity is investigated for electron swarms at high E/N. In the presence of ionization the experimental methods do not directly measure the electron drift velocity (v) as specified in the transport equation and calculated by solving Boltzmann's equation. The correlation factor relating the two velocities has been evaluated for four different experimental techniques. For E/N-282 Td the ratio v/vexp is as large as 1.53 for helium and 1.24 for hydrogen.