SMuK 2023 – scientific programme
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P: Fachverband Plasmaphysik
P 15: Laser Plasmas II/Low Pressure Plasmas and their Applications II
P 15.2: Talk
Thursday, March 23, 2023, 14:30–14:45, CHE/0089
Comparison between THz absorption spectroscopy and ps-TALIF measurements — •Jente R. Wubs1, Laurent Invernizzi2, Kristaq Gazeli2, Guillaume Lombardi2, Uwe Macherius1, Klaus-Dieter Weltmann1, and Jean-Pierre H. van Helden1 — 1Leibniz Institute for Plasma Science and Technology (INP), Greifswald, Germany — 2Laboratoire des Sciences des Procédés et des Matériaux (LSPM), CNRS, Université Sorbonne Paris Nord, Villetaneuse, France
Terahertz (THz) absorption spectroscopy with quantum cascade lasers has recently been developed and implemented as a new diagnostic technique for investigating atomic oxygen densities in plasmas. It is based on the detection of the 3P1 ← 3P2 fine structure transition at approximately 4.75 THz. This allows for direct measurements (i.e. no calibration procedure required) of absolute ground-state atomic oxygen densities. A possible way to validate this method is by a comparison with two-photon absorption laser-induced fluorescence (TALIF), as this is currently the most established method for measuring atomic oxygen densities. TALIF measurements were done in this case with a picosecond (ps) laser system and using a streak camera for detection. Both ps-TALIF measurements and THz absorption spectroscopy were performed on the same low-pressure capacitively-coupled radio frequency plasma generated in pure oxygen, for a variation of the applied power (20–100 W) and gas pressure (0.7–1.3 mbar). A comparison between resulting atomic oxygen densities as obtained with the two different diagnostics is presented in this contribution.