Kinetic study of the ClOO + NO reaction using cavity ring-down spectroscopy

Area of Science:

• Atmospheric Chemistry
• Chemical Kinetics
• Spectroscopy

Background:

• Peroxy radicals like ClOO play a role in atmospheric chemical processes.
• Understanding the reactions of ClOO is crucial for atmospheric modeling.
• Previous studies on ClOO reactions are limited.

Purpose of the Study:

• To determine the rate constant for the reaction between ClOO and NO.
• To measure the yield of nitrogen dioxide (NO2) from this reaction.
• To establish an upper limit for the reaction rate of ClOO with Cl2.

Main Methods:

• Cavity ring-down spectroscopy (CRDS) was employed.
• Experiments were conducted at total pressures of 50-150 Torr in an O2/N2 diluent.
• Temperatures ranged from 205-243 K.

Main Results:

• The rate constant for ClOO + NO was determined as (4.5 ± 0.9) x 10(-11) cm3 molecule(-1) s(-1) at 213 K.
• The yield of NO2 in the ClOO + NO reaction was 0.18 ± 0.02 at 213 K and 0.15 ± 0.02 at 223 K.
• An upper limit for the rate constant of ClOO + Cl2 was found to be < 3.5 x 10(-14) cm3 molecule(-1) s(-1) at 213 K.

Conclusions:

• The determined rate constant and NO2 yield provide key data for atmospheric models.
• The low reactivity with Cl2 suggests ClOO is less likely to form Cl2 directly.
• These findings contribute to understanding the atmospheric fate of ClOO and related peroxy radicals.