Kinetics of HO2 + HO2 → H2O2 + O2: Implications for Stratospheric H2O2

Christensen, L., M. Okumura, S. P. Sander, R. Salawitch, G. Toon, B. Sen, J. F. Blavier, and K. Jucks (2002), Kinetics of HO2 + HO2 → H2O2 + O2: Implications for Stratospheric H2O2, Geophys. Res. Lett., 29, 13-1-13-4, doi:10.1029/2001GL014525.

[1] The reaction HO2 + HO2 → H2O2 + O2(1) has been studied at 100 Torr and 222 K to 295 K. Experiments employing photolysis of Cl2/CH3OH/O2/N2 and F2/H2/O2/N2 gas mixtures to produce HO2 confirmed that methanol enhanced the observed reaction rate. At 100 Torr, zero methanol, k1 = (8.8 ± 0.9) 10−13 × exp[(210 ± 26)/T] cm3 molecule−1 s−1 (2σ uncertainties), which agrees with current recommendations at 295 K but is nearly 2 times slower at 231 K. The general expression for k1, which includes the dependence on bath gas density, is k1 = (1.5 ± 0.2) × 10−12 × exp[(19 ± 31)/T] + 1.7 × 10−33 × [M] × exp[1000/T], where the second term is taken from the JPL00-3 recommendation. The revised rate largely accounts for a discrepancy between modeled and measured [H2O2] in the lower to middle stratosphere.

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Tropospheric Composition Program (TCP)
Upper Atmosphere Research Program (UARP)