NEGATIVE DIFFERENTIAL CONDUCTIVITY OF ELECTRONS IN PURE RARE-GASES

A mechanism for negative differential conductivity (NDC) in pure rare gases is presented. The drift velocity of electrons in these gases has been calculated using the two-term expansion of the anisotropic elect ron energy distribution function in Legendre polynomials. In ionized r are gases (viz. Ar, Kr, and Xe), Coulombic collisions cause electron d rift velocity to become a decreasing function of the electric field fo r specific energy levels and over a certain range of electric field st rength. A detailed investigation of the effect of Coulomb interactions and electron collisions with excited atoms on NDC has been performed.