Greifswald 2024 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 14: Low Pressure Plasmas and their Application I

P 14.1: Hauptvortrag

Mittwoch, 28. Februar 2024, 11:00–11:30, WW 1: HS

Insights into the Non-Thermal Character of Molecular Plasmas from Optical Frequency Comb Spectroscopy — •Ibrahim Sadiek, Norbert Lang, and Jean-Pierre H. van Helden — Leibniz Institute for Plasma Science and Technology (INP)

Our ability to model, optimize and control plasma-activated chemical processes depends strongly on the knowledge of the absolute concentrations and temperatures of reactive species in the plasma, and their reaction kinetics. This knowledge can be acquired through absorption spectroscopy using continuous wave (CW) lasers. However, the narrow spectral tuning range of these CW lasers limits the number of detectable molecules and cannot provide precise information about the non-thermal nature of plasma-generated species, particularly the distribution of energy among different molecular degrees of freedom. We overcome this hurdle by using state-of-the-art optical frequency combs as diagnostic light sources. We develop and apply frequency comb-based detection techniques, offering a unique combination of broad bandwidth and high spectral resolution. This enables the simultaneous detection of multiple species in the plasma.

In this paper, we will present insights into the non-thermal nature of low-pressure molecular plasmas containing nitrogen, hydrogen, and methane through frequency comb-based Fourier transform spectroscopy measurements. This technique enables us to provide quantum-state-resolved knowledge of plasma-generated molecular species, thereby paving the way for precise modelling of plasma chemical processes.

Keywords: Optical Frequency Comb Spectroscopy; Non-Thermal Plasmas