Multi-Species Temperature Analysis in Methane Plasmas using Supercontinuum-Based Fourier Transform Spectroscopy

Plasma-based gas conversion is emerging as an alternative to thermal processes in the chemical industry. They can be driven by sustainable energy and highly reduce carbon dioxide emissions in chemical processes. Inside a plasma gas convertor, several reactions take place simultaneously: for instance, in a Methane plasma the dehydrogenation of methane and its conversion to larger hydrocarbons (e.g. ethane, ethylene, and acetylene). It is vital to study plasma-based gas conversions in order to get a detailed understanding of their dynamics and processes. In our previous work [1], we analysed the outflow of a plasma reactor to get an overview of the total conversion and the products formed. However, analysing compounds inside the plasma provides valuable information on the conversion dynamics, temperature-dependent rotational distribution, and vibrational excitation of the molecules during the discharge. Mid-infrared supercontinuum (SC) sources are novel tools for this application, as they provide a spatially coherent beam with a high brightness and broad spectral range. This allows to probe the plasma directly and observe full ro-vibrational bands of multiple molecular species and to obtain temperature information from the plasma.