Halogenated Methanes And Ethanes

Figures 4.44 and 4.45 show absorption spectra of some simple chlorofluoro-methanes and ethanes, respectively (Hubrich and Stuhl, 1980). Tables 4.37 and 4.38 give the recommended absorption cross sections for some of these compounds (DeMore et al., 1997). None of these compounds absorb in the actinic region above 290 nm, but do around 180-200 nm, wavelengths only found in the stratosphere. As discussed in Chapter f2, it is photolysis at these short wavelengths to generate atomic chlorine that is responsible, along with bromine and perhaps in some cases, iodine atoms, for the chain destruction of stratospheric ozone.

Tables 4.39 and 4.40 give the recommended absorption cross sections of some hydrochlorofluorocarbons at room temperature, and those of some brominated organics are found in Table 4.41 (DeMore et al., 1997).

Finally, alkyl iodides, some of which have natural sources, are of interest for both the troposphere and stratosphere. Figure 4.46 shows the absorption spectra of some simple alkyl iodides and Table 4.42 the absorption cross sections for CH3I (Roehl et al., 1997).

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