Influence of Electron Molecule Resonant Vibrational Collisions over the Symmetric Mode and Direct Excitation-Dissociation Cross Sections of CO2 on the Electron Energy Distribution Function and Dissociation Mechanisms in Cold Pure CO2 Plasmas.

A new set of electron-vibrational (e-V) processes linking the first 10 vibrational levels of the symmetric mode of CO2 is derived by using a decoupled vibrational model and inserted in the Boltzmann equation for the electron energy distribution function (eedf). The new eedf and dissociation rates are in satisfactory agreement with the corresponding ones obtained by using the e-V cross sections reported in the database of Hake and Phelps (H-P). Large differences are, on the contrary, found when the experimental dissociation cross sections of Cosby and Helm are inserted in the Boltzman equation. Comparison of the corresponding rates with those obtained by using the low-energy threshold energy, reported in the H-P database, shows differences up to orders of magnitude, which decrease with the increasing of the reduced electric field. In all cases, we show the importance of superelastic vibrational collisions in affecting eedf and dissociation rates either in the direct electron impact mechanism or in the pure vibrational mechanism.

Transport properties of local thermodynamic equilibrium hydrogen plasmas including electronically excited states.

A study of the dependence of transport coefficients (thermal conductivity, viscosity, electrical conductivity) of local thermodynamic equilibrium H2 plasmas on the presence of electronically atomic excited states, H(n), is reported. The results show that excited states with their "abnormal" cross sections strongly affect the transport coefficients especially at high pressure. Large relative errors are found when comparing the different quantities with the corresponding values obtained by using ground-state transport cross sections. The accuracy of the present calculation is finally discussed in the light of the selection of transport cross sections and in dependence of the considered number of excited states.

Electronically excited states and transport properties of thermal plasmas: the reactive thermal conductivity.

The role of excited states in affecting the transport of ionization energy in thermal plasmas in the temperature range 10,000 < or = T < or = 25,000 K is discussed by taking into account the dependence of diffusion cross sections on principal quantum number. The results show a strong effect at high pressure, while compensation effects reduce the role of excited states at atmospheric pressure. Extension of the results to nonequilibrium situations is discussed by presenting calculations of effective multicomponent diffusion coefficients. In this case also the presence of excited states dramatically affects these coefficients.