Chemiluminescence of the NI(b1Σ+ → X3Σ−) transition in active nitrogen reactions with aliphatic iodine compounds

The emission spectra from the reactions of C2H5I, C4H9I and CH2I2 with active nitrogen are observed in a flowing afterglow reactor. The experimental results show that these reactions exhibit identical chemiluminescence characteristics. Thirty-five spectral peaks in the 620-840 nm wavelength range are assigned to vibrational transitions of the NI(b1Σ+, v′ = 0 ∼ 6 → X3Σ−) band system. This is the first experimental evidence for the generation of excited state NI(b1Σ+) via chemical reactions in the gas phase. The possible formation mechanism of the electronically excited NI(b1Σ+) is proposed to be the reaction of N(2P) in active nitrogen with C2H5I, C4H9I, and CH2I2.