Vibrational-State-Resolved Measurements of Nitric Oxide for the Ground to Fourteenth Excited Vibrational State

A novel pathlength-amplified diagnostic strategy has been implemented to probe nitric oxide (NO) with high vibrational-state-specificity, covering states spanning the ground to the fourteenth excited vibrational states (v" = 0-14) and many rotational states. This new diagnostic strategy leverages a multipass ring amplifier to increase the absorbing pathlength in shock-tube experiments, thereby enabling extensive vibrational state resolution in high-temperature experiments. Demonstration of this diagnostic strategy was completed in reflected shock experiments probing a mixture of 6% oxygen (O2), 6% nitrogen (N2), and 88% argon (Ar) over three conditions spanning 3700-8300 K and 0.40-1.82 atm. Over this range of conditions, states up to v" = 9 are consistently resolved - even at low temperatures, and states up to v" = 14 are resolved at high temperature, enabling vibrational-state-resolved measurements of NO formed through reactions relevant to high-temperature air chemistry. Data included in this work demonstrate the vibrational-state-resolved absorbance measurements over the 1588.8-1581.0 cm-1 (6.294-6.325 um) range of the tunable diode laser system. From the scanned absorbance data, integrated absorbance areas are inferred, which are subsequently used to infer modal temperatures and vibrational-state-specific number densities. The current work compares integrated absorbance areas, modal temperatures, and vibrational-state-specific number densities to Park model simulations of the vibrational and chemical nonequilibrium processes for the 6% O2 /6% N2/Ar mixtures. Sensitivity and rate-of-production analysis were used to identify important reactions to improve model agreement with the data, although recommendations to improve air chemistry models will be completed in future work.