Infrared absorption spectroscopy and chemical kinetics of free radicals
Propargyl radical has recently attracted interest because of its possible role in combustion and soot formation. At high temperatures it is not easily destroyed by dissociation nor by reaction with oxygen thus, it has been observed in significant concentrations in numerous pyrolysis and oxidation processes. During the last year, we have obtained the high resolution spectrum of the v{sub 1} acetylenic CH stretch of propargyl radical (HCCCH{sub 2}) near 3322 cm{sup {minus}1} using infrared laser kinetic spectroscopy at Doppler limited resolution. Propargyl is prepared by flash photolysis of propargyl bromide (or propargyl chloride) at 193 nm (ArFexcimer) and its transient infrared absorption probed by a cw color center laser. We are beginning to investigate the kinetics of propargyl radical. The decay of the radical after the flash appears to be second order. The fine structure transition of the Br atom is accessible and when monitored under the same conditions appears to exhibit a simple first order decay suggesting that the Br atom is reacting with precursor propargyl bromide. Ketenyl radicals were produced by 193 nm excimer laser photolysis of ketene and probed with a tunable diode laser operating at 2014 cm{sup {minus}1}. Under these conditions, any singlet methylene which may be formed should react with the precursor, ketene, at a rate fast enough to ensure its total removal from the photolysis cell within 1 {mu}s. In the presence of 2 to 8 Torr of O{sub 2}, the ketenyl radical was observed to decay exponentially with time constants that ranged fro 20 to 5 {mu}s.
- Research Organization:
- Rice Univ., Houston, TX (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG05-85ER13439
- OSTI ID:
- 5184794
- Report Number(s):
- DOE/ER/13439-T3; ON: DE92014110
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
HALOGENATED ALIPHATIC HYDROCARBONS
PHOTOLYSIS
PROPARGYL RADICALS
CHEMICAL REACTION KINETICS
INFRARED SPECTRA
EXCIMER LASERS
KETENES
OXYGEN
PROGRESS REPORT
RADICALS
SOOT
ALKYL RADICALS
CHEMICAL REACTIONS
DECOMPOSITION
DOCUMENT TYPES
ELEMENTS
GAS LASERS
KINETICS
LASERS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
REACTION KINETICS
SPECTRA
400201* - Chemical & Physicochemical Properties
400500 - Photochemistry