Web Release Date: April 4,
Temperature Dependent Kinetics of the OH/HO2/O3 Chain Reaction by Time-Resolved IR Laser Absorption Spectroscopy
JILA, National Institute of Standards and Technology and University of Colorado, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0440
Received: September 30, 1999
In Final Form: January 11, 2000
Abstract:
This paper presents an extensive temperature dependent kinetic study of the catalytic HOx ozone cycle, (1)
OH + O3 
HO2 + O2 and (2) HO2 + O3 OH + 2 O2, based on time-resolved, Doppler limited direct
absorption spectroscopy of OH with a single mode (
= 0.0001 cm-1) high-resolution infrared laser. The
sum of the two chain rate constants, k1 + k2, is measured over the 190-315 K temperature range and can be
accurately described by an Arrhenius-type expression: k1 + k2 (cm3/s) = 2.26(40) × 10-12 exp[-976(50)/T].
These results are in excellent agreement with studies by Ravishankara et al. [J. Chem. Phys. 1979, 70, 984]
and Smith et al. [Int. J. Chem. Kinet. 1984, 16, 41] but are significantly higher than the values currently
accepted for atmospheric modeling. In addition, these studies also reflect the first such rate measurements to
access the 190-230 K temperature range relevant to kinetic modeling of ozone chain loss in the lower
stratosphere.
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