The ratio DT/µ between the transverse diffusion coefficient and the mobility has been measured as a function of the electric field to density ratio E/N, for K+ ions in all the noble gases at a temperature of 295 K and with an accuracy of 1% or better. In helium, the experimental data are in excellent agreement with theoretical values obtained from a recent ab initio potential. In the other gases, the experimental data have been used to estimate interaction potential parameters, using a modified Tang-Toennies-type potential model with hyperpolarizabilities included and a generalized Born-Mayer-type repulsive term.

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A procedure to separate the Townsend secondary electron emission coefficient γT into three components γTi, γTp and γTm due to ions, photons and metastables, respectively, is presented. The amplification system of ionization current in the form of a positive feedback amplifier with three feedback paths is analyzed in the frequency domain with the system functions given as the Fourier transform of the dynamic properties in the respective paths. The system functions in the three paths change values in different frequency ranges, and thus the three components are separated clearly. As a result of preliminary measurement electrode current in Ar, the separated values of γTi, γTp and γTm are presented and elucidated.

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