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Home > About us > Media > Archived news > 2017 > A better way to quantify atomic oxygen in reactive plasmas: LPP at Synchrotron SOLEIL

A better way to quantify atomic oxygen in reactive plasmas: LPP at Synchrotron SOLEIL

Oxygen atoms are a key reactive species in many O2-containing reactive environments such as plasmas for industrial surface treatments, atmospheric plasmas for medical treatment, and in combustion or the CO2 recycling. A number of methods have been developed to measure their concentration, important for understanding and controlling the behaviour of these systems. However, these methods (such as Two-Photon Laser-induced fluorescence, TALIF) have large uncertainties since they rely on successive tricky calibration procedures or questionable assumptions. Optical absorption spectroscopy is a more direct way to measure absolute concentrations with high accuracy. However, oxygen atoms only absorb light in the vacuum ultraviolet (VUV, below 200nm) spectral region; furthermore the well-known resonance lines at 130nm absorb so strongly in many circumstances that no light at all passes through the sample and they cannot be used.

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Left: DESIRS VUV beamline at SOLEIL synchrotron. Right: Abhyuday Chatterjee in front of the experimental set-up.

Abhyuday Chatterjee (LPP/Synchrotron SOLEIL joint PhD student, funded by Labex Plas@par, supervised by Jean-Paul Booth) has used the unique high-resolution (106) Fourier-transform spectrometer on the DESIRS VUV beamline at SOLEIL to measure oxygen atoms for the first time using a forbidden transition (100,000 times weaker than the resonance lines) at 135nm, giving absorptions of a few tens of percent, ideal for precise measurements. These measurements are part of a wider study of the reactivity of electrical discharges in oxygen, in collaboration with Olivier Guaitella and a team from Moscow State University via LIA KAPPA.


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Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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