Measurements and modeling of CO 4th positive (A–X) radiation

Abstract We present absolute intensity measurements of CO 4th positive emission from a CO2/Ar plasma jet produced using an atmospheric pressure plasma torch facility. The centerline temperature of the plasma jet is approximately 6300 K. A VUV emission spectroscopy system was adapted to the plasma torch facility to measure spectrally resolved emission down to 140 nm. The emission from the plasma in the VUV, UV and near IR is consistent with thermochemical equilibrium. Carbon lines in the UV and VUV are found to be optically thick and their amplitude is therefore substantially affected by the line broadening parameters used for the calculation. For the CO 4th positive emission, these measurements test the performance of various models for the electronic transition moment function (ETMF). These ETMFs are used to calculate sets of Einstein coefficients that are used by SPECAIR to calculate the spectrally resolved emission of the plasma for comparison with experiments. We find that the EMTF of Kirby and Cooper and Spielfiedel accurately reproduce the measured emission from 150–215 nm.