On improved understanding of plasma-chemical processes in complex low-temperature plasmas

• Published in: The European physical journal. D, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 2018-05, Vol.72 (5), p.1-11, Article 87
• Main Authors: Röpcke, Jürgen, Loffhagen, Detlef, von Wahl, Eric, Nave, Andy S. C., Hamann, Stephan, van Helden, Jean-Piere H., Lang, Norbert, Kersten, Holger
• Format: Article
• Language: English
• Subjects: Absorption spectra; Applications of Nonlinear Dynamics and Chaos Theory; Atomic; Chemical reactions; Diagnostic software; Diagnostic systems; Infrared lasers; Low temperature; Molecular; Molecular chains; Molecular gases; Optical and Plasma Physics; Optical emission spectroscopy; Physical Chemistry; Physics; Physics and Astronomy; Plasma; Plasma Physics; Plasmas (physics); Quantum Information Technology; Quantum Physics; Regular Article; Spectroscopy/Spectrometry; Spectrum analysis; Spintronics; Temperature; Temporal resolution; Topical Issue: Fundamentals of Complex Plasmas
• ISSN: 1434-6060; 1434-6079
• DOI: 10.1140/epjd/e2017-80363-7

Over the last years, chemical sensing using optical emission spectroscopy (OES) in the visible spectral range has been combined with methods of mid infrared laser absorption spectroscopy (MIR-LAS) in the molecular fingerprint region from 3 to 20 μ m, which contains strong rotational–vibrational absorption bands of a large variety of gaseous species. This optical approach established powerful in situ diagnostic tools to study plasma-chemical processes of complex low-temperature plasmas. The methods of MIR-LAS enable to detect stable and transient molecular species in ground and excited states and to measure the concentrations and temperatures of reactive species in plasmas. Since kinetic processes are inherent to discharges ignited in molecular gases, high time resolution on sub-second timescales is frequently desired for fundamental studies as well as for process monitoring in applied research and industry. In addition to high sensitivity and good temporal resolution, the capacity for broad spectral coverage enabling multicomponent detection is further expanding the use of OES and MIR-LAS techniques. Based on selected examples, this paper reports on recent achievements in the understanding of complex low-temperature plasmas. Recently, a link with chemical modeling of the plasma has been provided, which is the ultimate objective for a better understanding of the chemical and reaction kinetic processes occurring in the plasma. Graphical abstract