Reactive and nonreactive quenching of O(1D) by the potent greenhouse gases...

Zhao, Z., P. L. Laine, J. M. Nicovich, and P. Wine (2010), Reactive and nonreactive quenching of O(1D) by the potent greenhouse gases SO2F2, NF3, and SF5CF3, Proc. Natl. Acad. Sci., 107, 6610-6615, doi:10.1073/pnas.0911228107.

A laser flash photolysis–resonance fluorescence technique has been employed to measure rate coefficients and physical vs. reactive quenching branching ratios for O(1 D) deactivation by three potent greenhouse gases, SO2 F2 (k 1 ), NF3 (k 2 ), and SF5 CF3 (k 3 ). In excellent agreement with one published study, we find that k 1 (T) ¼ 9.0 × 10−11 exp ( þ 98∕T) cm3 molecule−1 s−1 and that the reactive quenching rate coefficient is k 1b ¼ (5.8 Æ 2.3) × 10−11 cm3 molecule−1 s−1 independent of temperature. We find that k 2 (T) ¼ 2.0 × 10−11 exp ( þ 52∕T) cm3 molecule−1 s−1 with reaction proceeding almost entirely (∼99%) by reactive quenching. Reactive quenching of O(1 D) by NF3 is more than a factor of two faster than reported in one published study, a result that will significantly lower the model-derived atmospheric lifetime and global warming potential of NF3 . Deactivation of O(1 D) by SF5 CF3 is slow enough (k 3 < 2.0 × 10−13 cm3 molecule−1 s−1 at 298 K) that reaction with O(1 D) is unimportant as an atmospheric removal mechanism for SF5 CF3 . The kinetics of O(1 D) reactions with SO2 (k 4 ) and CS2 (k 5 ) have also been investigated at 298 K. We find that k 4 ¼ (2.2 Æ 0.3) × 10−10 and k 5 ¼ (4.6 Æ 0.6) × 10−10 cm3 molecule−1 s−1 ; branching ratios for reactive quenching are 0.76 Æ 0.12 and 0.94 Æ 0.06 for the SO2 and CS2 reactions, respectively. All uncertainties reported above are estimates of accuracy (2σ) and rate coefficients k i (T) (i ¼ 1; 2) calculated from the above Arrhenius expressions have estimated accuracies of Æ15% (2σ).

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Upper Atmosphere Research Program (UARP)