Pressure-Dependent I-Atom Yield in the Reaction of CH2I with O2 Shows a Remarkable Apparent Third-Body Efficiency for O2
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- 作者：Haifeng Huang ; Arkke J. Eskola ; Craig A. Taatjes
- 刊名：The Journal of Physical Chemistry Letters
- 出版年：2012
- 出版时间：November 15, 2012
- 年：2012
- 卷：3
- 期：22
- 页码：3399-3403
- 全文大小：283K
- 年卷期：v.3,no.22(November 15, 2012)
- ISSN：1948-7185
文摘
The formation of I atom and Criegee intermediate (CH2OO) in the reaction of CH2I with O2 has potential relevance for aerosol and organic acid production in the marine boundary layer. We report measurements of the absolute yield of I atom as a function of pressure for N2, He, and O2 buffer at 298 K. Although the overall rate coefficient is pressure-independent, the I-atom yield, correlated with CH2OO, decreases with total pressure, presumably because of increased stabilization of CH2IOO. The extrapolated yield of the I + Criegee channel under tropospheric conditions is small but nonzero, 0.04. The zero-pressure limiting I-atom yield is unity, within experimental error, implying negligible branching to IO + CH2O. The apparent collision efficiency of O2 in stabilizing CH2IOO is a remarkable factor of 13 larger than that of N2, which suggests unusually strong interaction or possible reaction between the chemically activated CH2IOO# and O2.