Thermal-electron scattering by polar molecules

Experimental data for the temperature dependence of the drift velocity of thermal electrons travelling through polar gases were treated using effective range theory for electron scattering by polar molecules. The free parameter of the theory was chosen so that the theoretical temperature dependence of the drift velocity fitted the experimental data. Diffusion cross sections averaged over a Maxwellian distribution were calculated. The theoretical dependence of ( sigma d ) on the dipole moment D is more monotonic than that given by Christophorou and Pittman (1970) and does not show the jump near D cr =0.6395 au.