Different mechanisms of CO 2 dissociation, in discharge and post-discharge conditions, have been computed by performing a parametric numerical solution of the electron Boltzmann equation as a function of the electric field, the ionization degree and the vibrational temperatures and by considering elastic, inelastic, superelastic and electron electron collisions. Emphasis is given to the role of superelastic electronic and vibrational collisions in affecting the electron energy distribution function and relevant rates. The results show that, at low E/N values, the dissociation rates from pure vibrational mechanism can overcome the corresponding rates of electron impact dissociation. In any case, the electron impact dissociation rates are largely dependent on the transitions from excited vibrational levels.

A self-consistent time dependent model, based on the coupling between the Boltzmann equation for free electrons, the non equilibrium vibrational kinetics for the asymmetric mode of CO 2 and simplified global models for the dissociation and ionization plasma chemistry, has been applied to conditions which can be met under pulsed microwave (MW), dielectric barrier discharge (DBD) and nanosecond pulsed discharges (NPD). Under MW discharge type conditions, the selected pulse duration generates large concentration of vibrational excited states, which affects the electron energy distribution function (eedf) through the superelastic vibrational collisions. Moreover, in discharge conditions, plateaux appear in the vibrational distribution function (vdf) through the vibrational-vibrational up pumping mechanism, persisting also in the post discharge. In post discharge conditions, also the eedf is characterized by plateaux due to the superelastic collisions between cold electrons and the CO 2 electronic state at 10.5 eV. The plateau in vdf increases the dissociation of pure vibrational mechanism (PVM), which can become competitive with the dissociation mechanism induced by electron molecule collisions. The PVM rates increase with the decrease of gas temperature, generating a non-Arrhenius behaviour. The situation completely changes under DBD and NPD type conditions characterized by shorter pulse duration and higher applied E/N values. Under discharge conditions, both vdf and eedf plateaux disappear, reappering in the afterglow.

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A Boltzmann equation, in the presence of superelastic vibrational and electronic collisions and of electron-electron Coulomb collisions, has been solved in CO2 plasma in discharge and post discharge conditions. Superelastic vibrational collisions play an important role in affecting the electron energy distribution function (eedf) in a wide range of the reduced electric field E/N and of vibrational temperatures characterizing the vibrational modes of CO2. An important result is the dependence of fractional power losses and of the relevant rate coefficients on the vibrational temperatures of the system. Superelastic electronic collisions, on the other hand, are the main processes affecting eedf and related quantities in the post discharge conditions (i.e., E/N = 0). In particular at low vibrational temperatures, the superelastic electronic collisions form an important plateau in the eedf, largely influencing the rate coefficients and the fractional power transfer.