Ion concentrations in spark channels in hydrogen

Helium Afterglow and the Decay of the Electron Energy

“…3 Those effects which can act to increase the electron energy are: dissociative recombination involving an electron and the helium molecule ion, 4 and a superelastic collision involving a free electron and a helium atom in an excited state other than a metastable state. The ionizing collision between two helium atoms, one being initially in an excited state within 1.5 eV of the ionization level, 5 which results in the production of the helium molecule-ion and an electron, acts to raise the average electron energy only if the energy of the electron produced exceeds the average energy of the plasma electrons.…”

“…where n=electron density, g=the average fractional energy exchange in an electron-gas atom collision, v c = electron-atom collision frequency, e=electron energy, 4 The first term on the right of Eq. (1) represents the removal and redistribution of electrons due to diffusion; the second term represents electron-electron collisions; the third term is the electron-atom elastic recoil term 6 ; and the last term is a heating term resulting from the presence of metastable atoms.…”