Atmospheric Lifetimes of HFC-143a and HFC-245fa:  Flash Photolysis Resonance Fluorescence Measurements of the OH Reaction Rate Constants

1996 ◽  
Vol 100 (21) ◽  
pp. 8907-8912 ◽  
Author(s):  
Vladimir L. Orkin ◽  
Robert E. Huie ◽  
Michael J. Kurylo
Keyword(s):  
Rate Constants ◽  
Reaction Rate ◽  
Flash Photolysis ◽  
Resonance Fluorescence ◽  
Reaction Rate Constants ◽  
Fluorescence Measurements

scholarly journals Iron(III) hydroxocomplex - methyl viologen dication system as a prospective tool for determination of hydroxyl radical reaction rate constants with environmental pollutants

2021 ◽  
Author(s):  
Yuliya Tyutereva ◽  
Vyacheslav P. Grivin ◽  
Jing Xu ◽  
Feng Wu ◽  
Victor Plyusnin ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Rate Constants ◽  
Reaction Rate ◽  
Methyl Viologen ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Radical Reaction ◽  
Reaction Rate Constants ◽  
Wide Range

Abstract Reactivity of oxidative species with target pollutants is one of the crucial parameters for application of any system based on advanced oxidation processes (AOPs). This work presents new useful approach how to determine the hydroxyl radical reaction rate constants (kOH) using UVA laser flash photolysis technique. Fe(III) hydroxocomplex at pH 3 was applied as a standard source of hydroxyl radicals and methyl viologen dication (MV2+) was used as selective probe for •OH radical. Application of MV2+ allows to determine kOH values even for compounds which do not generate themselves optically detectable transient species in reaction with hydroxyl radicals. Validity of this approach was tested on a wide range of different persistent pesticides and its main advantages and drawbacks in comparison with existing steady-state and time-resolved techniques were discussed.

Flash photolysis under non-isothermal conditions

1967 ◽  
Vol 45 (20) ◽  
pp. 2369-2374 ◽  
Author(s):  
George Burns
Keyword(s):  
Temperature Rise ◽  
Rate Constants ◽  
Recombination Rate ◽  
Reaction Rate ◽  
Flash Photolysis ◽  
Bromine Atom ◽  
Fold Increase ◽  
Reaction Vessel ◽  
Reaction Rate Constants ◽  
Three Body

The temperature rise which accompanies every flash photolytic reaction interferes with, and often makes impractical, measurements of the reaction rate constants. This difficulty may be partly overcome if the whole reaction vessel is uniformly irradiated by both the photolytic and the analyzing flash lamps.A flash photolysis apparatus with these characteristics was used to study bromine atom recombination. A 10 to 15 fold gain in atomic concentration, which corresponds to a 100 to 225 fold increase in three-body recombination rate, compared with the work of previous authors, was achieved with this apparatus. The reaction rate constants were determined from the changes in absorption of Br2 at either 4 035 Å or at 4 980 Å. The recombination rate constant of bromine in an excess of helium at 90 ± 20 °C was found to be equal to (0.8 ± 0.3)109 l2 mole−2 s−1 (measured at 4 980 Å) and (0.5 ± 0.1)109 l2 mole−2 s−1 (measured at 4 035 Å). The results suggest that the technique herein described can yield meaningful data, even though the reaction was accompanied by a 105 °C temperature rise. There was little heat exchanged between the reacting gas and the walls of the reaction vessel. Consequently the reaction vessel behaved as an effective calorimeter throughout the reaction.

Thermal effects in flash photolysis with special reference to Br atom recombination

1968 ◽  
Vol 46 (20) ◽  
pp. 3229-3234 ◽  
Author(s):  
George Burns
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Thermal Effects ◽  
Reaction Rate ◽  
Flash Photolysis ◽  
Reaction Rate Constants ◽  
A Value ◽  
Recombination Rate Constant ◽  
Reaction Vessels

Thermal effects, which accompany flash photolyses, are known to interfere with the determination of reaction rate constants. There are two approximate models currently being used in literature to estimate the magnitude of these effects (1, 8). The first model (1) is the more widely accepted. It is based on the assumption that thermal effects are due to the cooling of reacting gas at the walls of the reaction vessel. The second model (8) is based on the assumption that thermal effects are due to nonuniformity in the concentrations of free radicals produced in flash photolysis; it neglects the heat exchange at the wall of the reaction vessel.It is shown that the second model can be used to calculate the magnitude of thermal effects in reaction vessels of reasonable length. The model was applied to calculate [Formula: see text], the rate constant for the reaction 2Br + Br2 → 2Br2. The value of [Formula: see text], is found to be very sensitive to the choice of model for thermal effects. At room temperature the most reasonable value of [Formula: see text], using the second model, is (4.3 ± 1.3) × 1010 l2 mole−2 s−1. This value agrees very well with independent determinations of [Formula: see text] using a stationary photochemical technique. The first model for treatment of thermal effects (1) was used previously to show that such effects do not influence the measured rates of chemical reactions, and calculations of rate constants using this model have not usually been attempted. In one case (5), however, the first model (1) for thermal effects was employed to calculate a value for [Formula: see text] which was found to be six times larger than our value. Consequently, the second model (8) appears to be a better approximation for quantitative evaluation of thermal effects.Using the raw data (8) and [Formula: see text] = 43 × 109 l2 mole−2 s−1, the value of kAr, the recombination rate constant of Br atoms in excess of argon, was found to be (3.0 ± 0.2) × 109 l2 mole−2 s−1, which agrees well with data available in the literature.

Measurement of the OH Reaction Rate Constants for CF3CH2OH, CF3CF2CH2OH, and CF3CH(OH)CF3

1999 ◽  
Vol 103 (15) ◽  
pp. 2664-2672 ◽  
Author(s):  
Kazuaki Tokuhashi ◽  
Hidekazu Nagai ◽  
Akifumi Takahashi ◽  
Masahiro Kaise ◽  
Shigeo Kondo ◽  
...  
Keyword(s):  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constants

scholarly journals PREDICTION OF REACTION RATE CONSTANTS OF HYDROXYL RADICAL WITH ORGANIC COMPOUNDS

2014 ◽  
Vol 59 (1) ◽  
pp. 2252-2259 ◽  
Author(s):  
ZHEN CHEN ◽  
XINLIANG YU ◽  
XIANWEI HUANG ◽  
SHIHUA ZHANG
Keyword(s):  
Hydroxyl Radical ◽  
Organic Compounds ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constants
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