Spectroscopic analysis of nonequilibrium excited state chemistry in a NASA arc jet

Michael W. Winter, Cidambi Srinivasan, Richard Charnigo, Dinesh K. Prabhu

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


To support the determination of total specific enthalpy of the plasma flow of the 60 MW Interaction Heating Facility at NASA Ames Research Center, spectroscopic measurements of nonequilibrium emission were performed in the freestream. In the visible to near-infrared wavelength region, the most prominent emission was from molecular N2, and in the ultraviolet region, the spectra were dominated by emission from molecular NO. The only atomic lines observed were those of copper (an erosion product of the electrodes). The bands of the First Positive System of N2 (B → A) differed significantly from spectra computed assuming only thermal excitation, suggesting overpopulation of the high vibrational states of the B state of N2. Populations of these high vibrational levels (peaking at vupper 13) of the N2 B state were determined by scaling spectra simulated for each upper vibrational state separately. The overpopulation of the high vibrational levels is assigned to inverse predissociation of neutral atoms into the N2 B state at vupper > 10 via level-crossing processes with the N2 A 0 5 Σg state. The vupper 12 and 13 emission has been used to determine N atom densities, which agree very well between the different experiment campaigns and with the computational-fluid-dynamics simulation of these flows.

Original languageEnglish
Pages (from-to)1088-1098
Number of pages11
JournalJournal of Thermophysics and Heat Transfer
Issue number4
StatePublished - 2018

Bibliographical note

Funding Information:
The experimental work and initial analysis were supported by NASA contracts NAS2-03/44 to the University Affiliated Research Center (UARC), University of California, Santa Cruz, NNA04BC25C to ELORET Corporation, and NNA10DE12C to ERC Inc., and by the NASA Strategic Capabilities Assets Program, which provided critical financial support of the arc jet operational capability at NASA Ames Research Center (ARC). The authors would like to thank George Raiche (Chief of the Thermophysics Facilities Branch, NASA ARC) for support of the experimental work and for access to the facilities, and Aga Goodsell and David Hash (former and current Chiefs, Reacting Flow Environments Branch, NASA ARC) for support of modeling and simulation aspects of the present work. Furthermore, the authors wish to acknowledge the support of Jay Grinstead, Vince Meglio, Imelda Terrazas-Salinas, Frank Hui, and Enrique Carballo and thank the arc jet crew for their professional and tireless effort to maintain and operate the arc jets under demanding schedule pressures. The authors also thank Chul Park (Korean Institute of Science and Technology) and Christophe Laux (École Centrale Paris) for numerous discussions about inverse predissociation and particularly Christophe Laux for providing reaction rates for the predissociation process.

Publisher Copyright:
Copyright © 2016 by Daniil Andrienko.

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Aerospace Engineering
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes
  • Space and Planetary Science


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