The excitation of N2(<i>B</i> 3Π<i>g</i>, <i>v</i>=1–12) in the reaction between N2(<i>A</i> 3Σ+<i>u</i>) and N2(<i>X</i>, <i>v</i>≥5)

Abstract

We have studied the excitation of N2(B 3Πg, v=1–12) in the interaction between N2(A 3Σ+u) and N2(X 1Σ+g, v≥5). The N2(A) and N2(B) are observed spectroscopically between 220 to 400 nm and 560 to 900 nm, respectively, while the N2(X,v) number densities are determined by metastable-helium Penning ionization. The experiments are performed in a discharge-flow reactor with separate discharge sources of N2(A), N2(X,v) and He*(23S). The excitation rate coefficient is (3±1.5)×10−11 cm3 molecule−1 s−1. Observations of N2(A) decay indicate that the N2(A) is removed by N2(X,v) with an apparent rate coefficient of about 3.5×10−12 cm3 molecule−1 s−1. The discrepancy between the excitation and removal rate coefficients probably results from N2(A) regeneration via cascade from the excited N2(B). The appearance of vibrationally excited N2(A) when N2(X,v) is added to a flow of N2(A, v=0) demonstrates this regeneration process. The reaction appears to be a transfer of electronic energy from the N2(A) to the N2(X,v) rather than an excitation of the N2(A) to N2(B) resulting from the input of energy from the N2(X,v).