On the Use of Measured Post-Discharge Gas Temperature Profiles in the Kinetic Modeling of the Pink Afterglow of Flowing N2 DC Discharges

• Published in: Brazilian journal of physics 2024-04, Vol.54 (2), Article 55
• Main Authors: Levaton, J., Klein, A. N., Amorim, J., Severo, J. H. F.
• Format: Article
• Language: English
• Subjects: Afterglows; Approximation; Discharge; Distribution functions; Electron states; Excitation; Gas temperature; General and Applied Physics; Mathematical analysis; Nitrogen; Numerical models; Optical emission spectroscopy; Physics; Physics and Astronomy; Rate constants; Temperature profiles; Vibrational states
• ISSN: 0103-9733; 1678-4448
• DOI: 10.1007/s13538-024-01430-0

In this study, we investigate the significance of utilizing measured post-discharge gas temperature profiles versus employing a representative constant gas temperature value in the kinetic modeling of the pink afterglow (PA) generated by flowing nitrogen DC discharges. Both approaches have been employed in the literature for PA kinetic modeling studies yielding reliable results. However, until now, no work has explored the kinetics aspects associated to these different methodologies in PA modeling. Firstly, we measure the spatial gas temperature variation in the post-discharge region using optical emission spectroscopy (OES). These spatial profiles are then converted into temporal profiles. We derive representative constant gas temperature values by calculating the mean gas temperature from these profiles. Subsequently we utilize a well-stablished kinetic numerical model for the PA, which calculate the densities of 15 distinct electronic states of nitrogen molecules, including the N 2 (X 1 Σ g + , 0 ≤ v ≤ 45) vibrational states, as functions of the post-discharge residence time. We analyze the post-discharge density profiles of certain singlet and triplet molecular states as well as ions, considering the different gas temperature approximations. The excitation rates of these molecular states are also studied. The N 2 (X 1 Σ g + ) vibrational distribution functions (VDF) are investigated. We have observed that the densities profiles and studied excitation rates are very similar for the two different assumptions, which validates the use of a representative constant gas temperature approximation in the absence of the measured temperature along the post-discharge. We observe global kinetic effects found for the different gas temperature approaches and it is demonstrated that these effects results from the VDFs behavior, which depends on the vibrational-vibrational (V-V) and vibrational-translational (V-T) rate constants that are functions of the gas temperature.