Showing papers by "Mitchio Okumura published in 2002"

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

Abstract: [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.