Quenching rate coefficients for N2(a′ 1Σ−u)

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Abstract
We have studied the kinetics of the lowest excited singlet state of molecular nitrogen, N2(a′ 1Σ−u,v=0), in a discharge flow reactor. The metastables were generated in a hollow cathode dc discharge through molecular nitrogen highly diluted in argon, and detected by VUV flourescence of the forbidden N2(a′ 1Σ−u–X 1Σ+g) band system. Observations of the equilibrium between the N2(a 1Πg) and N2(a′ 1Σ−u) states in our reactor indicate that the metastable has a radiative lifetime ≳23+11−6ms, assuming a radiative lifetime of 80+40−20μs for N2(a 1Πg). Rate coefficients for quenching by NO, CH4, CO, and N2O are approximately gas kinetic, those by H2, O2, and CO2 roughly tenth gas kinetic, and that by molecular nitrogen (1.9±0.5)×10−13 cm3 molecule−1 s−1. The interaction between N2(a′) and CO produced CO(A 1Π–X 1Σ) emission in about 21+10−8% of the quenching events.