Ulraviolet spectrum and reaction kinetics of the formyl radical
A transient ultraviolet absorption attributed to the formyl radical, HCO, was produced by the flash photolysis of water vapor in the presence of CO. For CO saturated with H/sub 2/O at a total pressure of 1 atm, the formation of HCO is complete within approx. 60 ..mu..s, after which it undergoes second-order decay, with k/epsilon(230 nm) = 1.5 +- 0.2) x 10/sup 7/ cm s/sup -1/. During the relatively slow formation reaction (H + CO(+M) ..-->.. HCO), the competing reaction H + HCO ..-->.. H/sub 2/ + CO is significant. By employing the H/sub 2/O + CH/sub 4/ system as an actinometer to determine the amount of H/sub 2/O dissociated by the flash (discussed elsewhere) and by computer modeling the observed formation and decay of HCO as a function of CO pressure, the following absolute rate constants were obtained: k/sub 3/(H + CO(+M) ..-->.. HCO) = (3.6 +- 0.9) x 10/sup 7/ M/sup -2/ s/sup -1/ for M = CO, (5.8 +- 0.6) x 10/sup 7/ M/sup -2/ s/sup -1/ for M = CH/sub 4/, and (3.8 +- 0.4) x 10/sup 7/ M/sup -2/ s/sup -1/ for M = H/sub 2/, k/sub 4/(HCO + HCO ..-->.. products) = (1.4 +- 0.3) x 10/sup 10/ M/sup -1/ s/sup -1/, and k/sub 5/(H +- HCO ..-->.. products) = (6.9 +- 1.7) x 10/sup 10/ M/sup -1/ s/sup -1/. The molar extinction coefficient epsilon(HCO, 230 nm) = 941 +- 171 M/sup -1/ cm/sup -1/.
- Research Organization:
- Oak Ridge National Lab., TN
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5378366
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 84:3; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400500* -- Photochemistry
ACYL RADICALS
ALKANES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CRYOGENIC FLUIDS
DATA
DATA FORMS
DECOMPOSITION
ELEMENTS
EXPERIMENTAL DATA
FLUIDS
FORMYL RADICALS
GASES
HYDROCARBONS
HYDROGEN
INFORMATION
ISOLATED VALUES
KINETICS
METHANE
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADICALS
REACTION KINETICS
SPECTRA
SYNTHESIS
ULTRAVIOLET SPECTRA
VAPORS
WATER VAPOR