Investigation of OH dynamics in the argon sensitized pulse radiolysis of water vapor
Reactions of OH radical were studied in systems containing 650-Torr Ar and from 0.5 to 9-Torr H/sub 2/O using the method of pulse radiolysis-absorption spectroscopy. It was found that initial concentrations of OH radical increased and the half-life for its loss decreased at higher water pressures. Dependence of OH half-life on OH concentrations occurs because homogeneous OH loss processes are second order in reaction intermediates, whose concentration increases with added H/sub 2/O. A contribution by water in chaperoning OH/OH and OH/H combination is also important. The kinetic scheme was examined with a Gear integrator. A good fit of the experimental rate data was obtained using literature values for rate constants of OH+OH, OH+H, and H+H reactions, when experimental zero-time absorbance values were converted to OH concentrations based on an extinction coefficient of 6.37 x 10/sup 4/ l mol/sup -1/ cm/sup -1/ at 309.5 nm. Using the same extinction coefficient, an alternative empirical reduction of rate data gives k-italic (apparent bimolecular) for loss of OH at 650-Torr Ar pressure of 5.06 x 10/sup -11/ cm/sup 3/ molec/sup -1/ s/sup -1/, consistent with literature rate constants within 10%. Dependence of OH yield on water concentration is interpreted on a two state model for argon precursor, involving short-lived (resonance state) Ar* (/sup 1/P-italic/sub 1/ and /sup 3/P-italic/sub 1/) and longer-lived (metastable) Ar** (/sup 3/P-italic/sub 2/ and /sup 3/P-italic/sub 0/). Adjustment of assumed initial Ar* and Ar** concentrations allowed prediction of measured OH concentrations within experimental error at all water pressures studied.
- Research Organization:
- Department of Chemistry, University of Florida, Gainesville, Florida 32611
- OSTI ID:
- 5501812
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 60:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HYDROXYL RADICALS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
WATER
DISSOCIATION
RADIOLYSIS
ABSORPTION SPECTRA
ARGON
ARGON IONS
BEAMS
ELECTRON COLLISIONS
PRESSURE EFFECTS
PULSE TECHNIQUES
ULTRAVIOLET SPECTRA
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COLLISIONS
DECOMPOSITION
ELEMENTS
FLUIDS
GASES
HYDROGEN COMPOUNDS
IONS
KINETICS
NONMETALS
OXYGEN COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RARE GASES
REACTION KINETICS
SPECTRA
YIELDS
400600* - Radiation Chemistry