Modeling of the charge transfer afterglow excited by intense electrical discharges in high pressure helium nitrogen mixtures

In this work, we report the study of bimolecular and termolecular charge transfer and Penning ionization reactions in He–N2 mixtures excited by repetitive 3 kA, 7 ns duration discharges. He(2 3S) destruction frequencies have been determined from measurements of the optical absorption of the 2 3S→3 3P helium transition and were found to correlate with the late-time decay rate of the N2+(B 2Σu→X 2Σg) fluorescence. The much more intense early-time fluorescence was ascribed to charge transfer from He2+. The values found for the bimolecular and termolecular charge transfer reactions were, respectively, (1.1±0.1)×10−9 cm3 s−1 and (1.36±0.20)×10−29 cm6 s−1, while the corresponding values for the Penning reactions were (7.6±0.4)×10−11 cm3 s−1 and (3.3±0.3)×10−30 cm6 s−1. Branching ratios for producing the N2+(B 2Σu) state in these reactions are discussed. A comprehensive kinetic model of the He–N2 afterglow has been formulated which was able to reproduce all the experimental data obtained as functions of helium pressure over the range 310–760 Torr and as functions of the partial pressure of nitrogen from 5–500 mTorr.