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.

A time of flight pulse technique has been used for the measurement of the ratio of radial diffusion coefficient to mobility (Dr/ mu )d for electron swarms in helium, argon, neon and krypton. The experimental range for helium and argon is 56.5

Calculations have been made for the electron swarm parameters in mixtures of argon and metal vapour for E/N varying from 2.82 to 282 Td. Three metal vapours, namely sodium, potassium and caesium, have been investigated for conditions in which the concentrations of metal vapour varied from 0.001% to 20%. The results have shown that for a small percentage of metal vapour both the ionisation coefficient and the drift velocity have higher values than in either pure argon or pure metal vapour. The mean energy and the ratio of radial diffusion coefficient to mobility have both shown monotonic variations at a fixed E/N from the higher values in pure argon to the lower values in pure metal vapour. The radiation emission has also been computed. It is observed that for a range of E/N determined by the percentage of metal vapour, that most of the swarm energy is emitted as metal vapour radiation.

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.