  This work explores the effect of N2 addition on CO2 dissociation and on the
vibrational kinetics of CO2 and CO under various non-equilibrium plasma
conditions. A self-consistent kinetic model, previously validated for pure CO2
and CO2-O2 discharges, is further extended by adding the kinetics of N2. The
vibrational kinetics considered include levels up to v = 10 for CO, v = 59 for
N2 and up to v1 = 2 and v2 = v3 = 5, respectively for the symmetric stretch,
bending and asymmetric stretch modes of CO2, and account for electron-impact
excitation and de-excitation (e-V), vibration-to-translation (V-T) and
vibration-to-vibration energy exchange (V-V) processes. The kinetic scheme is
validated by comparing the model predictions with recent experimental data
measured in a DC glow discharge operating in pure CO2 and in CO2-N2 mixtures,
at pressures in the range 0.6 - 4 Torr (80.00 - 533.33 Pa) and a current of 50
mA. The experimental results show a higher vibrational temperature of the
different modes of CO2 and CO and an increased dissociation fraction of CO2,
that can reach values as high as 70%, when N2 is added to the plasma. On the
one hand, the simulations suggest that the former effect is the result of the
CO2-N2 and CO-N2 V-V transfers and the reduction of quenching due to the
decrease of atomic oxygen concentration; on the other hand, the dilution of CO2
and dissociation products, CO and O2, reduces the importance of back reactions
and contributes to the higher CO2 dissociation fraction with increased N2
content in the mixture, while the N2(B3Pg) electronically excited state further
enhances the CO2 dissociation.
