Hydrogen peroxide photodissociation

Uncertainties in Photochemical Models. The ability of photochemical models to accurately predict HO concentrations is undoubtedly more reliable in clean vs. polluted air, since the number of processes that affect [HO ] and [H02 ] is much greater in the presence of NMHC. Logan et al (58) have obtained simplified equations for [HO ] and [HO2 ] for conditions where NMHC chemistry can be ignored. The equation for HO concentration is given in Equation E6. The first term in the numerator refers to the fraction of excited oxygen atoms formed in R1 that react to form HO J refers to the photodissociation of hydrogen peroxide to form 2 HO molecules other rate constants refer to numbered reactions above. 

Most of the recent reviews on photodissociation dynamics have had an extensive section on the earlier work on water (2-4, 7,20) because it is an important component on the earth s atmosphere. In this section we shall concentrate on the more recent work on water and hydrogen peroxide, since 0H(X2II) is amenable to laser detection. 

Crowell RA, Lian R, Sauer MC, Oulianov DA, Shkorob IA (2004) Geminate recombination of hydroxyl radicals generated in 200 nm photodissociation of aqueous hydrogen peroxide. Chem Phys Lett 383 481-485... 

The absorption cross section of hydrogen peroxide is shown in Figure 4.39. In the spectral domain which is important in the stratosphere, absorption cross section measurements have been made by Schurgens and Welge (1968) from 120 to 200 nm, Holt et al. (1948) and Holt and Oldenberg (1949) from 185 to 253 nm, and Urey et al. (1929) from 215 to 380 nm. More recent measurements include those of Lin et al. (1978), Molina and Molina (1981), Nicovich and Wine (1988), and Vaghjiani and Ravishankara (1989). The cross sections vary slightly with temperature. The photodissociation quantum efficiency is believed to be unity. 

Photodissociation of Hydrogen Peroxide Solution Singlet or Triplet Precursor ... 

Primary process (I) is the dominant photodissociation pathway for hydrogen peroxide at all wavelengths of sunlight available within the troposphere (Vaghjiani and Ravishankara, 1990 Vaghjiani et al., 1992 Schiffman et al., 1993). 

It is also formed in the photodissociation of matrix-isolated methyl nitrate that yields either HNO2 (hydrogen nitryl) or imine peroxide HNOO. ... 

Alkoxysulfinyl radicals ROSO are closely related to alkyl sulfinyls and were first identified in solutions of dialkyl sulfites under UV irradiation either in the presence or absence of peroxides [42]. The reactions involved in generation of ROSO species under these conditions involve either direct photodissociation or /[-scission followed by subsequent hydrogen abstraction to form an unstable substituted alkyl radical (the methyl derivative is shown as an example) ... 

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