Pressure dependence of the reactions of HO2 with Cl and ClO
Abstract
The kinetic behaviour of HO2 and ClO radicals in the photolysis of Cl2–H2–O2–N2 mixtures, in the total pressure range 50–760 Torr, has been investigated by molecular modulation–u.v. absorption. Rate coefficients for the reactions Cl + HO2→ HCl + O2(3a), Cl + HO2→ OH + ClO (3b) and ClO + HO2→ HOCl + O2(6) were obtained. At 308 K the preferred values were k3a= 4.4 × 10–11 cm3 molecule–1 s–1, k3b= 9.4 × 10–12 cm3 molecule–1 s–1 independent of pressure, but owing to uncertainties in the calculated [Cl] these values may be, respectively, low and high by a factor of two. A corresponding uncertainty exists in the pressure dependence. The value of k6=(6.2 ± 1.5)× 10–12 cm3 molecule–1 s–1 at 308 K was well determined and was independent of pressure in the range 50–760 Torr.