Variation with Electron Energy of the Collision Cross Section of Helium for Slow Electrons

The method of interaction of microwaves in gaseous discharge plasmas has been applied to a determination of the variation of the effective collision cross section for momentum transfer, $q_m$, of helium atoms with electrons having energies from 0.04 to 0.4 ev. Under our experimental conditions with electron densities ≳${10}^{10}$ electrons/cc, appropriate charge interactions have been considered. The mean fraction of excess energy loss of slow electrons upon collision, $G$, was found to be ∼2.7×${10}^{-4\mathrm{}}$, the expected $\frac{2m}{M}$ value.