Polarization spectroscopy for quantitative analysis of atmospheric CO2 and air plasma flows.

This article demonstrates the feasibility of polarization spectroscopy as a diagnostic tool for quantitative analysis of atmospheric pressure plasma conditions. Atmospheric pressure air and CO 2 plasma flows created in a microwave-powered plasma torch are investigated. A detailed line-by-line simulation approach is employed to interpret the polarization spectra recorded in the resonator of the plasma torch. The line-by-line code for the simulation of polarization spectroscopy of O 2 Schumann–Runge has been developed and verified with measurements in atmospheric pressure O 2 plasma for a previous study. In this study, this simulation code for O 2 absorption is used to model the polarization spectra measured in CO 2 plasma and determine the inner energy distribution of the molecules for the first time. The resulting vibrational and rotational temperatures are T v i b = 6115 K and T r o t = 2660 K. In order to simulate measurements in air plasma, the line-by-line code is extended to enable two-species modeling using O 2 Schumann–Runge as well as NO γ absorption. The new two-species simulation approach allows for the determination of the relative number density n O 2 / n NO = 1500 ± 100. This paper clearly demonstrates the value of polarization spectroscopy as a quantitative measurement technique for atmospheric pressure plasma applications. [ABSTRACT FROM AUTHOR]