Non-Equilibrium Ionization of Cesium-Seeded Helium Using Three-Energy Level and One or More Electron Group Models

The results of two sets of calculations of the non-equilibrium ionization electron density based on a three-energy level model of the cesium seed atom is compared with the widely used approach to the calculation of non-equilibrium ionization electron density by substituting the electron temperature in Saha's thermal equilibrium ionization equation. In one set of calculations the rate coefficients for both collisional and radiative reaction processes are included, with the rate coefficients for radiative decay from the first j-excited state doublet of cesium to the ground state level including or ignoring the effect of imprisonment of resonance radiation. In the other set of calculations the photo-ionization and photo-excitation rate coefficients are excluded. Both sets of calculations, yield electron densities significantly lower than those given by Saha's equation and show the trend for the electron densities to approach those given by Saha's Eq. at very high electron temperatures where the collisional processes dominate. The calculations which included the rate coefficients for photo-ionization and photo-excitation and which also took into account the effect of imprisonment of resonance radiation yielded the better results.