Hydrogen Peroxide H2O2 , Methyl Hydroperoxide CH3OOH

7 Hydrogen Peroxide (H2O2), Methyl Hydroperoxide (CH3OOH) 

Hydrogen peroxide H2O2 is formed by the radical termination reaction HO2 + HO2, and exists in the troposphere generally at the mixing ratio in order of ppbv. Since H2O2 is water soluble, it is removed by the dissolution into cloud and fog water, while photolytic reaction is another important removal process. Methyl hydroperoxide CH3OOH also exists in the whole region of the troposphere in natural atmosphere as an oxidation product of methane. Its photolytic reaction is important as its removal process, and also as a radical source in the upper troposphere. 

The absorption cross sections of H2O2 are known to have temperatme dependence due to the effect of transition from vibronic excited states in the electronic ground state (Nicovich and Wine 1988 Knight et al. 2002),and their temperature dependence at 260 nm is given by Nicovich and Wine (1988) as a function of wavelength. 

The absorption spectrum of CH3OOH bears a resemblance to H2O2, and a continuum in which the absorption cross sections decreases monotonically from ultraviolet to near ultraviolet region as shown in Fig. 4.22. There has been considerable uncertainty in the absorption cross sections of CH3OOH due to the effect of impurities, and the recommended values of NASA/JPL Evaluation No. 17 based on Vaghjiani and Ravishankara (1989) are cited in Table 4.18. 

The photolytic processes of H2O2 and CH3OOH in near ultraviolet region are 

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