Tuning of Conversion and Optical Emission by Electron Temperature in Inductively Coupled CO₂ Plasma

This paper focuses on how the electron temperature and other plasma properties affect optical emission and CO₂ conversion in CO₂ plasma. Such plasma-mediated reactions can enable efficient CO₂ reuse. We study CO₂ and CO plasmas generated by inductively coupled radiofrequency power (30–300 W) at low pressures (6–400 Pa). By varying the argon admixture, we can study the effect of the electron temperature, T_e, on the conversion and emission properties using optical emission spectroscopy, mass spectrometry, and electrical probe measurements. Importantly, we can observe several parameters simultaneously: T_e, CO₂ conversion, chemiluminescence from CO₂, and dissociation products and optical emission from several atomic and CO transitions and from the C₂ Swan system. On the basis of these results, we establish a correlation between T_e, the CO₂ conversion, and the optical emission spectra. A low T_e enhances CO₂ conversion and Swan band emission. In contrast with published studies, our results show that the CO₂ and C₂ vibrations are not in local equilibrium. This means that the vibrational temperatures of CO₂ and C₂ should differ.