Simultaneous O Atom nsTALIF and NO nsLIF Imaging Strategy to Expedite Characterization and Numerical Validation of High Enthalpy Plasma Flows

In this work, results from a laser-induced fluorescence (LIF) approach capable of simultaneously measuring ground-state information of multiple species using a single tunable laser source. This method employs a spectrally narrow tunable laser to excite atomic oxygen (via nsTALIF) and molecular nitric oxide (via nsLIF) in high-enthalpy air plasma flows produced by the University of Illinois, Urbana-Champaign 350 kW Plasmatron X Facility. Two gated ICCD cameras with with different phosphor, intensifier, and filter configurations were utilized to image the emission along the laser beam, enabling the simultaneous acquisition of full jet radial profiles for both species. This work demonstrate that significant LIF signals of free-jet oxygen atoms (O) and nitric oxide molecules (NO) can be simultaneously captured by probing the O atom 3p² transition and nearby high rotational number transitions in the NO (A-X) band. The extracted ro-translational temperatures for O and NO were relatively consistent, and the radial relative species number densities followed expected trends and computational models. These findings suggest that the simultaneous species LIF technique holds considerable promise for high-enthalpy flow studies, investigations into gas-surface interaction chemistry, and the validation of numerical models requiring a robust understanding of spatial enthalpy distributions.