Kinetics of the reactions of Cl atoms with CH3Br and CH2Br2

✍ Scribed by Tomasz Gierczak; Leah Goldfarb; Donna Sueper; A. R. Ravishankara

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 660 KB
• Volume: 26
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550260705

✦ Synopsis

Abstract

The rate coefficients for the reactions of Cl atoms with CH~3~Br, (k~1~) and CH~2~Br~2~, (k~2~) were measured as functions of temperature by generating Cl atoms via 308 nm laser photolysis of Cl~2~ and measuring their temporal profiles via resonance fluorescence detection. The measured rate coefficients were: k~1~ = (1.55 ± 0.18) × 10^−11^ exp{(−1070 ± 50)/T} and k~2~ = (6.37 ± 0.55) × 10^−12^ exp{(−810 ± 50)/T} cm^3^ molecule^−1^ s^−1^. The possible interference of the reaction of CH~2~Br product with Cl~2~ in the measurement of k~1~ was assessed from the temporal profiles of Cl at high concentrations of Cl~2~ at 298 K. The rate coefficient at 298 K for the CH~2~Br + Cl~2~ reaction was derived to be (5.36 ± 0.56) × 10^−13^ cm^3^ molecule^−1^ s^−1^. Based on the values of k~1~ and k~2~, it is deduced that global atmospheric lifetimes for CH~3~Br and CH~2~Br~2~ are unlikely to be affected by loss via reaction with Cl atoms. In the marine boundary layer, the loss via reaction (1) may be significant if the Cl concentrations are high. If found to be true, the contribution from oceans to the overall CH~3~Br budget may be less than what is currently assumed. © 1994 John Wiley & Sons, Inc.