A study of background emissions enhancements in nitrogen afterglows, due to addition of discharged O2, in connection with the reactions {N2 (A3Σu+, υ) + O(3P)}, {O2 (a1Δg) + N(4S)} and {O2 (a1Δg) + N2 (A3Σu+)}

Abstract

Intensity enhancement due to the addition of discharged O2 is examined for background N2 (B Πg → A3Σu+) emissions in various flowing nitrogen afterglows. Possible implications are reported for the experimentally determined rate constants for the reactions {N2 (A3Σu+, υ) + O(3P)}, and {O2 (a1Δg) + N(4S)}, as a result of the present study. The present, as well as previously reported, N2 (B Πg → A3Σu+) emissions intensity enhancements suggest complementary conclusions. Previous differences in experimental results reported for the {O2 (a1Δg) + N(4S)} reaction [based on studies observing the decay of either O2 (a1Δg) molecules or N(4S) atoms alone] are reconciled by a unifying additional interpretation. This interpretation leads to a rate constant estimate for the energy transfer reaction, {O2 (a1Δg) + N(2(A3Σu+)}, deduced to account for the above N2 (B3Πg → A3Σu+) emissions intensity enhancements.

Theoretical Study of the Reactions of Methane and Ethane with Electronically Excited N2(A3Σu+)

“…Nitrogen molecule in the lowest triplet electronic state, N 2 (A 3 Σ u + ), has rather high radiative lifetime (∼1 s), because the radiative transition to the ground state N 2 (X 1 Σ g + ) is spin forbidden. , At the same time, the electronic excitation energy of the N 2 (A 3 Σ u + ) molecule ( T e = 6.22 eV) , is greater than the typical bond energy for the most di- and polyatomic molecules, including hydrocarbon ones. Elementary processes, involving the metastable N 2 (A 3 Σ u + ) molecule, come into play in the upper and middle atmosphere of Earth and of Saturnian satellite Titan, − in the hypersonic flows under re-entry conditions, , in the nitrogen and nitrogen–oxygen discharge plasma − and in plasma chemistry. , It should be emphasized that the phosphorescence at the transition A 3 Σ u + → X 1 Σ g + of N 2 , corresponding to the Vegard–Kaplan band system, was well studied in the past both experimentally and theoretically. , The emission of the Vegard–Kaplan band is important for aurora and laboratory investigations of the processes with active nitrogen.…”

Reaction of the N Atom with Electronically Excited O2 Revisited: A Theoretical Study

“…Meanwhile, for a number of problems and issues, such as reacting gas flow behind the strong shock wave and in the expanding nozzle, ,− atmospheric chemistry, − electric discharge chemistry, − plasma chemistry and plasma processing, , laser-induced and plasma-aided combustion, ,,− are associated with appreciable electronic excitation of the gaseous air components. At the same time, it is known that electronic excitation can substantially alter molecular properties, especially, reactivity, ,− as a result of which the use of nonequilibrium O 2 (air) discharge plasma containing highly reactive electronically excited molecules [essentially, O 2 (a 1 Δ g ) and N 2 ( A 3 Σ u + )] can promote ignition and combustion of various fuel/O 2 (air) mixtures. ,,− …”

“…Let us emphasize that the kinetics of the outlined elementary reactions, besides the immense relevance for plasma- and laser-stimulated chemical processes, ,,,,,, is also important for refining the kinetic models of shock-induced air plasma ,,− , and atmospheric chemistry. ,,,,, As well, it is likely that the careful study of these processes could shed light on the reasons for the above-mentioned discrepancy between theory and experiment concerning the reaction . Of considerable interest for the applications alluded to is also the nascent energy distribution in reaction products (the way the chemical energy released is partitioned into the different product degrees of freedom, viz.…”