Effect of Oxygen and Hydrogen Atoms on the Vibrational Distribution of N2(B 3Π) in the Nitrogen Afterglow

Abstract

The effect of oxygen, hydrogen, and deuterium atoms and of molecular O2, D2, and SF6 on the vibrational population distribution of N2(B 3Π) in nitrogen afterglows has been investigated for pressures between 0.01 and 2.0 torr. At N2 pressures less than 0.1 torr, these atoms cause preferential population in the lower vibrational levels, and all levels appear to have a high rotational temperature. Emission from the N2 first-positive system is increased by as much as a factor of 60 by the addition of oxygen atoms, and there is a pronounced population maximum at υ′ = 6 with smaller maxima at υ′ = 2, 4, 8, and 12. Hydrogen and deuterium atoms decrease the populations in high vibrational levels and have small population peaks at υ′ = 2 and 12.

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+)}

“…None of these studies has taken into account any possible effects of the observed "N 2 (B→A) increases" [10][11][12] on these experimental chemical reaction rate constants. Similar "N 2 (B→A) increases" were reported [13][14] in the 1960s. The "N 2 (B→A) increases" were initially ascribed to such factors as the effect of O( 3 P) atoms on the vibrational redistribution of N 2 (B 3 Π g ) via formation of N 2 (A 3 Σ + u ), that collisionally crosses into the N 2 (B 3 Π g ) state [10][11][12][13][14].…”

“…These enhancements occurred when a stream of microwave (mw) discharged O 2 was mixed with a stream of mw discharged nitrogen without a catalyst and at much higher pressures than ever before [10][11][12]. The recently studied enhancements, as well as those in previous studies [13,14,15], were uniformly ascribed, in references [10][11][12], to the interaction between excited N 2 , (also described as N * 2 for electronically excited N 2 , and as N ♣ 2 for vibrationally excited N 2 , respectively), and electronically excited O 2 , (also O * 2 ), that led to collisional intersystem crossing into the N 2 (B 3 Πg) state [10]. On the basis of the available evidence, the N 2 (A 3 Σu + ) state was explicitly included [10,12], contrary to its specific exclusion [5].…”

“…The present investigation critically examines new and previous [1][2][3][4][5][6][7][8][9][10][11][12] data from extensive research on emissions and energy transfer in a flowing afterglow of active nitrogen and oxygen, when discharged O 2 is added to it. It reports on an analysis of previous experiments [2,13] on enhanced spectra; and on unifying arguments about the role of possible nitrogen and oxygen species in the "N 2 (B→A) increases". A unifying mechanism is also deduced for the "N 2 (B→A) increases" caused by discharged O 2 , both with and without a catalyst, previously reported [10][11][12][13][14].…”

“…In an early article [13] [17] in the assumed reaction {O 2 (a 1 ∆g) + N}, henceforth called reaction aN, which will be further reconsidered in this work.…”

“…The "N 2 (B→A) increases" were initially ascribed to such factors as the effect of O( 3 P) atoms on the vibrational redistribution of N 2 (B 3 Π g ) via formation of N 2 (A 3 Σ + u ), that collisionally crosses into the N 2 (B 3 Π g ) state [10][11][12][13][14]. N 2 (A 3 Σ + u ) was assumed to be produced either catalytically [14], due to surface-catalyzed formation of excited NO, in early work, and, in later work due to N atom recombination by the O( 3 P) atomconditioned surface; or without a metallic catalyst [13].…”