NEGATIVE DIFFERENTIAL CONDUCTIVITY OF ELECTRONS IN HE-XE AND HE-KR MIXTURES

The drift velocity of electrons in binary inert gases has been calculated with the Davydov distribution function obtained with the two-term expansion of the anisotropic distribution function in Legendre polynomials. For binary mixtures of helium with either xenon or krypton, the drift velocity was found to decrease with increasing electric field for specific mole fraction and electric field strengths, that is, a negative differential conductivity (NDC) was observed. The effect was found not to occur for other inert gas mixtures. A detailed study of the effect for several model systems together with an asymptotic analysis of the field variation of the electron mobility is presented. © 1990.