Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Mechanical Engineering

Major Professor

Zhili Zhang

Committee Members

Rao V. Arimilli, William R. Hamel, Yanfei Gao


This thesis includes two main parts: (I) The CH3[methyl radical] detection in methane/air flames and (II) the rotational temperature measurement of O2[molecular oxygen] in a variety of environments by using coherent microwave Rayleigh scattering from resonance enhanced multiphoton ionization (Radar REMPI).

In first the part, from Chapter I to Chapter III, the methyl radical detection and quantitative measurements have been conducted in hydrocarbon flame with one-dimensional and two-dimensional spatial-resolved concentration distribution. Due to the proximity of the argon resonance state (4+1 REMPI by 332.5 nm) with the CH3 state (2+1 REMPI by 333.6 nm), in situ calibration with argon was performed to quantify the absolute concentration of CH3. The numerical simulations performed using the detailed kinetic mechanism of GRI-3.0 were also provided in the comparison between experimental results and numerical calculations. The details of experimental results and discussions have been reported in Chapter I, II, and III.

In the second part, the O2 rotational temperature has been measured using Radar REMPI. The Rydberg state C3Π[C3Pi] has been selected as the intermediate state of O2 in the 2+1 REMPI process, the rotational-resolved spectra from two-photon C3Π←←X3Σ[X3Sigma] transition have been obtained in a variety of conditions from room temperature (294K) to flame temperature (1658 K). The temperature extraction based on the Boltzmann plots has been used in Chapter IV~VI. In Chapter VII, measurements of rotational temperatures of molecular oxygen have been demonstrated based on the empirical analyses of the O2 spectra without the requirement of highly resolved rotational features using (1) linewidth fitting, (2) linear fitting, and (3) area fitting methods. In the last chapter, the O2 REMPI spectral model has been built up to accomplish the simulation calculations. The temperature information has been determined based on the comparison between experimental results and REMPI spectral simulations. The O2 REMPI spectral model has been first reported in the community as a demonstration for the rotational temperature measurement of molecular oxygen with a wide temperature measuring range.

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