Temperature, density, and electric-field effects on electron mobility in nitrogen vapor

A detailed study of the effect of temperature on electron mobility in low-density nitrogen gas has revealed a Ramsauer-Townsend minimum in the scattering cross section at 1.7×{}10^-16 cm² and 15±{}2 meV. The cross sections at ε<0.010 eV are much larger than those previously reported. Energy gained by the electrons from the field is imparted to the molecules mainly through inelastic collisions, down to mean energies of a few meV. With increasing gas density the temperature coefficient θn,T=(∂log(μn)∂logT)n,T near the vapor-liquid coexistence curve increases from -0.6 at the low-density limit and 80 K to zero at nnc≥0.5 and TTc>0.97. While nnc increases from 0.5 to 1.0 along the coexistence curve, the density-normalized mobility μn decreases from 14 to 1.0 (10²² molecule/cm Vs) and the electric-field effect dμdE changes sign from negative to positive. This behavior at high densities is attributed to electron capture, ${e}^{{-}}+{N}₂{}{N}₂{{}}^{{-}N2}{({N}₂)}₂{{}}^{{-}N2}$ and so on. The capture coefficient ${{ν}}ₐ$ decreases with increasing electron energy.