Определение отношения коэффициентов диффузии и подвижности электронов в случае благородных газов

Abstract

Taking elastic scattering into consideration, but neglecting inelastic collision, with the application of the Boltzmann transport equation the equilibrum distribution function of electrons has been calculated with a view to determine the energy dependence of the diffusion cross section. In the knowledge of the equilibrium distribution function the ratioD/μ of diffusion coefficient to mobility was determined. In the case of very low electric field strength the calculated equilibrium distribution function gives the Maxwell-Boltzmann distribution andD/μ=kT/e. With increasing electric field strength the equilibrium distribution function passes through an intermediate distribution and finally gives the distribution calculated byMorse, Allis andLamar. The ratioD/μ increases with the electric field strength. With the assumption of a diffusion cross section independent from energy in the case of higher electric field strengths the ratio increases linearly with the field strength. The results have been applied to the calculation of the dependence of the ratioD/μ on electric field strength for helium and neon gases. The results have been compared with measured data.