SAMOP 2021 – scientific programme

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MO: Fachverband Molekülphysik

MO 9: Poster 2

MO 9.7: Poster

Friday, September 24, 2021, 17:30–19:30, P

Quantitative detection of C₂H₂ in a dusty plasma environment using sensitive mid-IR frequency modulation spectroscopy — •Mithun Pal¹, Michael Stuhr¹, Nancy Faßheber¹, Andreas Petersen², Franko Greiner², and Gernot Friedrichs¹ — ¹Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Germany — ²Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Germany

We report both the implementation of single- and two-tone mid-IR frequency modulation (FM) schemes to measure acetylene (C₂H₂) concentration transients in a low-temperature dusty plasma arising from a RF discharge in low-pressure argon with C₂H₂ admixture. The key underlying concept of the FM technique is to shift the detection bandwidth of the optical spectrometer to a high-frequency region, where conventional technical noise from the laser source and experimental environment become negligible. Moreover, due to the derivative nature of the acquired spectra, broadband background absorption and scattering from interfering species or particles are efficiently suppressed. In order to quantify the concentration of acetylene, we experimentally probed the P(25)e rovibrational transition of C₂H₂ at 3233.08 cm⁻¹, originating from the fundamental vibrational band ν₃ (asymmetric C-H stretch). Additionally, we monitored the periodic C₂H₂ dynamics under variable discharge conditions to demonstrate the high potential of transient mid-IR FM spectroscopy to gain insight into the kinetics of the nanoparticle nucleation, growth, and precipitation.