Combined Absorption and Emission Study of Air Species in NASA EAST

Abstract

A suite of tunable diode laser absorption spectroscopy (TDLAS) diagnostics targeting rovibrational states of nitric oxide (NO) in the mid-infrared (MIR) and electronic states of atomic oxygen (O) and nitrogen (N) in the near-IR (NIR) was combined with optical emission spectroscopy (OES) for overlapping wavelengths at the NASA Electric Arc Shock Tube (EAST) facility for three selected high-temperature air experiments. Absorption features were probed at rates up to 1 MHz to provide quantitative, time-resolved measurements of temperature and species number density profiles behind incident shocks, enabling comparisons to spatially-resolved emission measurements, with the two typically agreeing within their respective uncertainties. Inferred time-histories are further compared to incident shock simulations from two one-dimensional models - one leveraging the Park two-temperature rates and the other more recent rate values - as well as the Data Parallel Line Relaxation (DPLR) code. For the two low-velocity cases (3.81 and 3.98 km/s) in which NO is probed, inferred temperatures are typically well-captured by all three models, although the NO number densities show stronger variation, agreeing better for the model with updated NO formation and dissociation rates. Finally, one high-velocity case (7.03 km/s) demonstrates the simultaneous resolution of three O-atom and six N-atom electronic states, with all states showing a steady increase in number density over time - possibly due to shock trajectory effects. Together, this combined absorption and emission study demonstrates resolution of many states of nonequilibrium air species, while directly comparing ground- and excited-state populations via the combined diagnostic strategy.

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Cite

BibTeX RIS

BibTeX

@misc{streicher2026combined,
  title = {{Combined Absorption and Emission Study of Air Species in NASA EAST}},
  author = {Jesse W. Streicher and Efaine Chang and Dylan L. Drescher and Christopher L. Strand and Ronald K. Hanson and Andrea Fagnani and Augustin C. Tibere-Inglesse and Brett A. Cruden},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.19346},
  eprint = {2610.19346},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.19346},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Combined Absorption and Emission Study of Air Species in NASA EAST
AU  - Jesse W. Streicher
AU  - Efaine Chang
AU  - Dylan L. Drescher
AU  - Christopher L. Strand
AU  - Ronald K. Hanson
AU  - Andrea Fagnani
AU  - Augustin C. Tibere-Inglesse
AU  - Brett A. Cruden
PY  - 2026
DA  - 2026/10/14
PB  - arXiv
DO  - 10.48550/arxiv.2610.19346
UR  - https://arxiv.org/abs/2610.19346
AB  - A suite of tunable diode laser absorption spectroscopy (TDLAS) diagnostics targeting rovibrational states of nitric oxide (NO) in the mid-infrared (MIR) and electronic states of atomic oxygen (O) and nitrogen (N) in the near-IR (NIR) was combined with optical emission spectroscopy (OES) for overlapping wavelengths at the NASA Electric Arc Shock Tube (EAST) facility for three selected high-temperature air experiments. Absorption features were probed at rates up to 1 MHz to provide quantitative, time-resolved measurements of temperature and species number density profiles behind incident shocks, enabling comparisons to spatially-resolved emission measurements, with the two typically agreeing within their respective uncertainties. Inferred time-histories are further compared to incident shock simulations from two one-dimensional models - one leveraging the Park two-temperature rates and the other more recent rate values - as well as the Data Parallel Line Relaxation (DPLR) code. For the two low-velocity cases (3.81 and 3.98 km/s) in which NO is probed, inferred temperatures are typically well-captured by all three models, although the NO number densities show stronger variation, agreeing better for the model with updated NO formation and dissociation rates. Finally, one high-velocity case (7.03 km/s) demonstrates the simultaneous resolution of three O-atom and six N-atom electronic states, with all states showing a steady increase in number density over time - possibly due to shock trajectory effects. Together, this combined absorption and emission study demonstrates resolution of many states of nonequilibrium air species, while directly comparing ground- and excited-state populations via the combined diagnostic strategy.
ER  -

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