Average Energy Variations and Trapping of Electrons in the Resonances of Rare Gases

The effect of resonant elastic collisions of electrons in He on their “exact” mean energy variation for free path in the presence of a d.c. electric field is analysed. Different values of E/N and both isotropic and anisotropic initial velocity distributions, just after collision, are considered. It is shown that for sufficiently elevated values of E/N a necessary condition for electron (resonance) trapping becomes satisfied. This result is discussed in the light of an interpretative model advanced to explain some electroluminescence phenomena in rare gases.