title: Flame temperature measurements by radar resonance-enhanced multiphoton ionization of molecular oxygen.
abstract: Here we report nonintrusive local rotational temperature measurements of molecular oxygen, based on coherent microwave scattering (radar) from resonance-enhanced multiphoton ionization (REMPI) in room air and hydrogen/air flames. Analyses of the rotational line strengths of the two-photon molecular oxygen C(3)Π(v=2)←X(3)Σ(v'=0) transition have been used to determine the hyperfine rotational state distribution of the ground X(3)Σ(v'=0) state. Rotationally resolved 2+1 REMPI spectra of the molecular oxygen C(3)Π(v=2)←X(3)Σ(v'=0) transition at different temperatures were obtained experimentally by radar REMPI. Rotational temperatures have been determined from the resulting Boltzmann plots. The measurements in general had an accuracy of ~±60 K in the hydrogen/air flames at various equivalence ratios. Discussions about the decreased accuracy for the temperature measurement at elevated temperatures have been presented.
authors.affiliation: Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wu
authors.forename: Jordan
authors.initials: J
authors.lastname: Sawyer
authors.forename: Zhili
authors.initials: Z
authors.lastname: Zhang
authors.forename: Steven F
authors.initials: SF
authors.lastname: Adams
mesh_terms: D000465:Algorithms; D005390:Fires; D007477:Ions / Q000032:analysis; D008872:Microwaves; D010100:Oxygen / Q000032:analysis*; D017785:Photons; D011825:Radar; D012542:Scattering, Radiation; D013057:Spectrum Analysis / Q000379:methods*; D013696:Temperature; D013816:Thermodynamics; D062125:Thermometry / Q000295:instrumentation*; D014732:Vibration
chemical_list: D007477:Ions; D010100:Oxygen