Atmospheric reactions of the H02radical studied by laser magnetic resonance spectroscopy

Abstract

Measurement of the rotational spectra of HO$_{2}$ and HO by laser magnetic resonance has been used to determine rate coefficients for reactions of HO$_{2}$ in a fast flow system at low pressures and ambient temperatures. Processes of atmospheric importance were studied and the rate coefficients obtained were: O + HO$_{2}$ = HO + O$_{2}$, (4) $k_{4}$ = (3.1 $\pm $ 1.0) $\times $ 10$^{-11}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$, HO + HO$_{2}$ = H$_{2}$O + O$_{2}$, (8) $k_{8}$ = (5.1 $\pm $ 1.7) $\times $10$^{-11}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$, NO + HO$_{2}$ = NO$_{2}$ + HO, (2) $k_{2}$ = (8.2 $\pm $ 2.4) $\times $10$^{-12}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$, HO$_{2}$ + Cl = HCl + O$_{2}$, (17) $k_{17}$ = (4.1 $\pm $ 1.4) $\times $10$^{-11}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$, HO$_{2}$ + Cl = HO + ClO, (17a) $k_{17a}\leq $ 3 $\times $10$^{-13}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$, HO$_{2}$ + SO$_{2}$ = HO + SO$_{3}$, (21) $k_{21}\leq $ 2 $\times $10$^{-17}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$, HO$_{2}$ + SO$_{2}$ + He = HO$_{2}$SO$_{2}$ + He, (21a) $k_{21a}\leq $ 4 $\times $10$^{-34}$ cm$^{6}$ molecule$^{-1}$ s$^{-1}$, HO$_{2}$ + CO = HO + CO$_{2}$, (22) $k_{22}\leq $ 2 $\times $10$^{-17}$ cm$^{3}$ molecule$^{-1}$ s$^{-1}$, HO$_{2}$ + CO + He = HCO$_{3}$ + He, (22a) $k_{22a}\leq $ 4 $\times $10$^{-34}$ cm$^{6}$ molecule$^{-2}$ s$^{-1}$. The disproportionation of two HO$_{2}$ radicals was shown to proceed more slowly in argon carriers at total pressures around 2 Torr than had been reported at higher total pressures. Upper limits for $k_{19}$ were HO$_{2}$ + HO$_{2}$ = H$_{2}$O$_{2}$ + O$_{2}$ (19) found to lie in the range (7.5 $\pm $ 5.0) $\times $ 10$^{-13}$ cm$^{3}$ molecule$^{-1}$ s $^{-1}$.