Experimental measurements of the drift velocity and the ratio of longitudinal diffusion coefficient to mobility for electrons have been obtained for the range of 2.8<or=E/N<or=566 Td for argon and 14<or=E/N<or=849 Td for krypton (1 Td=10-17 V cm2). The results obtained from Monte Carlo simulation have been compared with the present and previously obtained data and a good fit has been achieved for the entire range of E/N. The simulation also produced results for the ionisation coefficient and the ratio of radial diffusion coefficient to mobility and these values have also been compared with other theoretical and experimental values, where available. The mean energy has also been computed and compared with the experimental breakdown voltage. This comparison has shown that equilibrium conditions exist in the region in which the present measurements have been made. As a result of this investigation, two sets of cross-sections are given which accurately simulate electron swarm parameters in argon and krypton respectively.

The Monte Carlo technique has been used to simulate the electron swarm motion in carbon dioxide and nitrogen, and electron swarm parameters have been evaluated in the range of E/N varying from 14 to 3000 Td (1 Td=10-17 V cm2). These parameters, namely ionisation coefficient, drift velocity, ratios of both radial and longitudinal diffusion coefficients, to mobility (also attachment and dissociation coefficients in the case of carbon dioxide) have been compared with the available experimental data. A set of elastic and inelastic cross-sections has been collected for each gas such that the computed and experimental values gave good agreement for each swarm parameter over the entire E/N range. In addition the percentage of energy lost by different types of inelastic collisions and also the mean swarm energy have been given as a function of E/N for each gas.

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

Experimental measurements of the drift velocity and the ratio of longitudinal diffusion coefficient to mobility for electrons have been obtained for the range of 25<or=E/N<or=848 Td for oxygen and 0.28<or=E/N<or=848 Td for methane (1 Td=10-17 V cm2). The results obtained from a Monte Carlo simulation have been compared with the present and previously obtained data and a good fit has been achieved for the entire range of E/N. As a result of this investigation, two sets of cross sections are given which accurately simulate electron swarm parameters in oxygen and methane. The simulation also produced results for the ionisation coefficient and the ratio of radial diffusion coefficient to mobility and these values have also been compared with other theoretical and experimental values, where available. The mean energy has also been computed.

Measurements of the ratio of radial diffusion coefficient to mobility, Dr/ mu , have been obtained for carbon monoxide, nitrogen and hydrogen. A pulse technique has been used covering a wide range of E/N from 28 to 5650 Td. The values of Dr/ mu vary between 0.8 and 17 eV in carbon monoxide, between 1.2 and 16 eV in nitrogen and between 1 and 12 eV in hydrogen. Comparison has been made with results of a Monte Carlo computer simulation. For all the gases, fair agreement has been obtained with the theory except for the highest of range E/N. This discrepancy has been explained by the presence of a non-equilibrium electron energy distribution in the experimental measurements.