This work investigates the high-temperature vibrational relaxation and decomposition of nitric oxide (NO) diluted in nitrogen (N2) to target the NO–N2 rates relevant to high-temperature air, thereby building off the argon (Ar) experiments investigated in Part I. [J. W. Streicher et al., “High-temperature vibrational relaxation and decomposition of shock-heated nitric oxide. I. Argon dilution from 2200 to 8700 K,” Phys. Fluids 34, 116122 (2022)] Again, two continuous-wave ultraviolet laser diagnostics were used to obtain quantum-state-specific time histories of NO in high-temperature shock-tube experiments, including absorbance (α) in the ground vibrational state of NO, translational/rotational temperature (Ttr), and number density of NO (nNO). The experiments probed mixtures of 2% and 0.4% NO diluted in either pure N2 (NO/N2) or an equal parts N2/Ar mixture (NO/N2/Ar). The NO/N2 experiments spanned initial post-reflected-shock conditions from 1900–7000 K and 0.05–1.14 atm, while the NO/N2/Ar experiments spanned from 1900–8200 K and 0.11–1.52 atm. This work leveraged two vibrational relaxation times from Part I (τVTNOAr and τVTNONO) and extended measurements to include the vibrational–translational and vibrational–vibrational relaxation times with N2 (τVTNON2 and τVVNON2). Similarly, this work leveraged the four rate coefficients from Part I (kdNOAr, kdNONO, kfN2O, and kzNOO) and extended measurements to include NO dissociation with N2 (kdNON2). A few studies have directly inferred these rates from experiments, and the current data differ from common model values. In particular, τVTNON2 differs slightly from the Millikan and White correlation, τVVNON2 is four times slower than Taylor et al.'s inference, and kdNON2 is four times slower than the Park two-temperature model. The unique experimental measurements and dilution in N2 in this study significantly improve the understanding of the vibrational relaxation and decomposition of NO in high-temperature air.

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