Active nitrogen and oxygen: Enhanced emissions and chemical reactions

Data and unifying arguments are presented regarding previously unreported intensity enhancements of nitrogen first positive band system (1pbs) emissions, N2(B3Πg,ν′)→N2(A3Σu+,ν″)+hν, by adding discharged O2 to a flowing afterglow of active nitrogen and oxygen. The nitrogen 1pbs emissions intensity enhancements are observed at a broader spectral range (and at higher resolution, in some cases) than previously, even from high vibrational N2(B3Πg, ν′) states reported here for the first time. The arguments presented affect the validity of certain conclusions reported during the last 45 years in studies of energy transfer between nitrogen species, like N(4S) and N2(A3Σu+), and oxygen species, like O(3P) and O2(a1Δg). They also provide a different interpretation of previously reported pertinent experimental data. Previous and new experimental data are utilized, in order to resolve the mechanism of the reported intensity enhancements of N2 1pbs background afterglow emissions caused by discharged oxygen. The involvement of N2(A3Σu+) in the reported intensity enhancements of N2 1pbs emissions, recently inferred, is further supported by the analysis of previous and present experimental results. The mechanism of the reported N2 1pbs emissions intensity enhancements appears to be due to an elusive homogeneous collisional energy transfer from O2(a1Δg) to N2(A3Σu+). Estimation of the reaction rate constant for the {O2(a1Δg)+N2(A3Σu+)} chemical reaction is based on previously unreported, and on published, data on the O2(a1Δg) and N2(A3Σu+) decays in a nitrogen afterglow, and is appended. As a result of the aforesaid energy transfer between O2(a1Δg) and N2(A3Σu+), that is supported by additional experiments in this work with discharged gas mixtures of (Ar + N2), and with gas mixtures of (N2 and discharged Ar), the reported reaction rate constants values for the chemical reactions {N2(A3Σu+,ν)+O(3P)} and {O2(a1Δg) + N(4S)}, need reassessment. Reassessment is also needed for the reported O(1S) product formation yield of the chemical reaction {N2(A3Σu+,ν=0)+O(3P)}. A potential change in the intensity of airglow, sprite, and low-altitude auroral N2(B3Πg) emissions is suggested as a result of the inferred energy transfer {O2(a1Δg)+N2(A3Σu+)}.