Multi-Diagnostics Study of Hydrocarbon-Containing Low-Temperature Plasma focusing on the Oxidation of Reactive Species

Highly reactive particles dictate the behavior of hydrocarbon-containing low-temperature plasma, used in processes like chemical vapor deposition and the dry-reforming of methane [1,2]. The high reactivity and resulting significance for reaction pathways on the one hand, and their low density and lack of fundamental data, like reaction rates, on the other hand are like two sides of the same coin. The scarcity of fundamental data is addressed by a multi-diagnostics approach, employing both in situ and ex situ spectroscopic techniques. Particularly, unprecedented in situ synchrotron VUV absorption spectroscopy on the δ1(0-0) Rydberg band of CH3 located at 150nm enables tracking of this critical radical with high absolute sensitivity. Optical emission spectroscopy and ex situ IR absorption spectroscopy complement the data with information about excited species in the plasma and long-lived species in the spatial post-discharge. In the wide parameter scan conducted, the oxygen admixture variation is emphasized, allowing to study the oxidation of CH3 and other species all the way from the oxygen-limited regime to full oxidation. The data serves as basis for a model of the chemistry. This research enhances our understanding of plasma behavior and opens avenues for optimizing industrial plasma processes.

[1] Baratte et al. (2024). Plasma Chem. Plasma Process., 44(3), 1237-1286

[2] Garcia-Soto et al. (2024). Plasma Chem. Plasma Process., 44(3), 1287-1326