  This work explores the effect of O2 addition on CO2 dissociation and on the
vibrational kinetics of CO2 and CO under various non-equilibrium plasma
conditions. A self-consistent model, previously validated for pure CO2
discharges, is further extended by adding the vibrational kinetics of CO,
including electron impact excitation and de-excitation (e-V),
vibration-to-translation relaxation (V-T) and vibration-to-vibration energy
exchange (V-V) processes. The vibrational kinetics considered include levels up
to v = 10 for CO and up to v1=2 and v2=v3=5, respectively for the symmetric
stretch, bending and asymmetric stretch modes of CO2, and accounts for e-V, V-T
in collisions between CO, CO2 and O2 molecules and O atoms and V-V processes
involving all possible transfers involving CO2 and CO molecules. The kinetic
scheme is validated by comparing the model predictions with recent experimental
data measured in a DC glow discharge, operating at pressures in the range 0.4 -
5 Torr (53.33 - 666.66 Pa). The experimental results show a lower vibrational
temperature of the different modes of CO2 and a decreased dissociation fraction
of CO2 when O2 is added to the plasma but an increase of the vibrational
temperature of CO. On the one hand, the simulations suggest that the former
effect is the result of the stronger V-T energy-transfer collisions with O
atoms which leads to an increase of the relaxation of the CO2 vibrational
modes; On the other hand, the back reactions with O2 contribute to the lower
CO2 dissociation fraction with increased O2 content in the mixture.
