The ratio DT/μ for electrons in a 0.5% hydrogen-krypton mixture

The ratio DT/μ for electrons in a 0.4673%H2-99.5327%Kr mixture at 295 K has been measured by the Townsend-Huxley method in order to obtain data for use in the derivation of the momentum transfer cross section for krypton. The values of E/N and pressures used ranged from 0.025 to 1.4 Td and 13.43 to 68.16 kPa respectively. At a given value of E/N and pressure the derived values of DT/μ were found to depend on the choice of the mathematical expression which relates the measured current ratio to DT/μ. The present measurements provide data which are much more sensitive to the momentum transfer cross section for krypton than are drift velocity values and should therefore significantly assist in reducing the uncertainty in the derived cross section. The present values also appear o be the most rigorous test available of the adequacy of the model on which the Lowke relation is based. The failure of this model and the success of the Huxley relation raises fundamental questions concerning the treatment of boundary conditions and non-hydrodynamic effects in the theoretical description of the behaviour of electrons in gases. 21 refs., 3 tabs., 5 figs