The case for CO₂ decomposition in plasma through vibrational activation: a closer look at the vibrational kinetics in a high excitation regime

Dissociation of CO₂ in plasmas has been shown to be theoretically and empirically promising. However, the bridge between throughput and underlying mechanisms is often brittle. Because at typical plasmas conditions vibrational excitation is often the dominant energy channel, it is natural to wonder how that excitation mechanism relates to the ultimate goal of dissociation. In this work we investigate the role of vibrationally activated CO₂ in its decomposition by modelling and studying CO₂ gas in a high vibrational excitation regime sustained by high power MIR lasers. We pinpoint and quantify three important aspects for maintaining vibrational non-equilibrium: energy deposited per molecule, time window of energy deposition and selectivity to the asymmetric stretch mode. Preliminary results show that, to achieve fully vibrational assisted dissociation, about 0.1 eV has to be deposited within 100 mean collisions of a CO₂ molecule (or about 25 ns at 1bar and 300K), after which the system starts to relax and efficiency of dissociation through vibrational ladder climbing starts plateauing. If the energy input is not fully selective to the asymmetric stretch mode, as would be the case in plasma activation of CO₂, more energy per molecule is needed in a shorter time window.