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Dissertation Information for YongMan Choi

NAME:
- YongMan Choi

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2004)

ADVISORS:
- Ming-Chang Lin

COMMITTEE MEMBERS:
- Myron J. Kaufman
- James T. Kindt

MPACT Status: Fully Complete

Title: Experimental and computational studies of phenyl radical reactions with combustion species and some thermal and photochemical reactions of nitrosobenzene

Abstract: Kinetics and mechanisms for the reactions of phenyl (C 6 H 5 ) radical with four small carbonyl compounds, CH 2 O, CH 2 CO, CH 3 CHO, and CH 3 COCH 3 , have been determined experimentally by means of cavity ringdown spectroscopy (CRDS) over the temperature range 298-500 K at 40-75 Torr pressure. These data are relevant to the interpretation of soot formation kinetics since the small carbonyl compounds may actually co-exist with the phenyl radical in the incipient stages of soot buildup via polycyclic aromatic hydrocarbons. In particular, in order to elucidate their mechanisms and to extrapolate our measured rate constants to high temperatures for combustion modeling applications, we have carried out extensive quantum-chemical and statistical-theory calculations. A similar kinetic and mechanistic analysis for the reaction of C 6 H 5 with HNO, a known combustion intermediate, has also been performed. The thermal and photochemical decomposition of nitrosobenzene (C 6 H 5 NO), the precursor of the phenyl radical employed in the present studies, have been investigated computationally with emphasis on the determination of the energy-dependent fragmentation rate constants from its ground electronic and the two low-lying excited states which are accessible to both thermal and photochemical excitation at 248 and 193 nm. The result of this calculation confirms the experimentally observed unusually large A-factor (>10 17 s -1 ) for the thermal decomposition of C 6 H 5 NO as well as the result of a recent molecular beam study with multimass ion-imaging detection that the photo-dissociation of C 6 H 5 NO at 248 and 193 nm generates exclusively the C 6 H 5 + NO products, despite the fact that another pair of products, C 6 H 4 + HNO, is also energetically accessible. In addition, a detailed kinetic modeling for the reaction of photodissociated C 6 H 5 NO in the presence of an excess amount of CH 3 CHO under CRDS conditions has been performed to illustrate the validity of the pseudo-first order kinetics of the C 6 H 5 decay observed experimentally. Finally, the novel thermal redox reactions of C 6 H 5 NO with NO x (x = 1 or 2) investigated experimentally by the Pyrolysis/Fourier transform infrared (P/FTIR) spectroscopic technique have been computationally modeled by quantum-chemical and statistical-theory calculations.

MPACT Scores for YongMan Choi

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2008-03-22 16:13:59

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