Electronically excited oxygen atoms

D) is an electronically excited oxygen atom. It can decay back to a ground state oxygen atom ( P) (which will regenerate an ozone molecule), or else it can react with water to produce two OH radicals ... 

A major source of OH in both clean and polluted air is the photodissociation of 03 by actinic UV radiation in sunlight to produce an electronically excited oxygen atom, O( D),... 

TABLE 4-2 Threshold Wavelengths for the Production of Ground-State or Electronically Excited Oxygen Atoms from 02 Photolysis"... 

Furthermore, because these reactions result in the effective removal of NOx from ozone production, by removing N02, the model also predicts that O, concentrations will decrease. Figure 7.17, for example, shows the model results for the ratio of O, (R0i) with the heterogeneous removal of N03 and N2Os included to that without these aerosol reactions. In some locations, the 03 concentrations are predicted to be as much as 30% lower than they would have been in the absence of the heterogeneous reactions. Because 03 is also the major OH source on a global scale, via its photolysis to electronically excited oxygen atoms, O( D), which react in part with gas-phase water, this also decreases the predicted OH levels. 

It is now known that the quantum yield of (9b) is less than 1% (Greenblatt and Ravishankara, 1990). However, NzO is still the major source of oxides of nitrogen in the stratosphere (McElroy and McConnell, 1971) via its minor (compared to loss by photolysis) reaction with electronically excited oxygen atoms,... 

The presence of 03 in the troposphere leads to the formation of OH radicals through the photolysis of 03 at wavelengths 290-350 nm to form the electronically excited oxygen atom, 0(JD), which either reacts with water vapor or is deactivated by reaction with 02 and N2 to the ground state oxygen atom, (03P) (Atkinson, 1995 Atkinson et al., 1997). 

Nitrogen. The overwhelming fraction of electronically excited oxygen atoms formed in the photolysis of O3 in the atmosphere are deactivated by collisions with N2 and O2, with kNj [N2]/ko. [O2] = 2.4. This de-... 

A study of the analogous reaction of O ( D ) with alcohols (Goldstein and Wiesenfeld, 1983), while of no direct atmospheric importance, reveals interesting details concerning the reactive characteristics of electronically excited oxygen atoms and provides information about the unimolecular dissociation dynamics of chemically activated molecules. In the generic case of O ( D2) reaction with methanol, a variety of reactive pathways are available ... 

When ozone absorbs a photon in the near-ultraviolet with a wavelength shorter than 315 nm, an electronically excited oxygen atom is produced ... 

A secondary destruction path is provided by the reaction with the electronically excited oxygen atom 0(1D). For example, in the case of CFC-12,... 

The green color observed in aurora borealis is produced by the emission of a photon by an electronically excited oxygen atom at 558 nm Calculate the energy difference between the two levels involved in the emission process. 

The electronically excited oxygen atom reacts with alkanes, the dominant reaction mechanism being the insertion of this atom into the C-H bond, thus yielding chemically activated alcohol followed by fragmentation [8c,d]. 

The photodecomposition of ozone may form electronically excited oxygen atoms, 0( D), and excited molecular oxygen with absorption of the 193-nm radiation (Reaction [13.35]). The 0( D) species formed in Reaction [13.35] is much more reactive than the ground-state oxygen atoms [0( P)] ... 

The production of OH radicals by the reaction of H2O with the electronically excited oxygen atoms 0( D) formed in the photolysis of ozone (O3) is the most important reaction in the natural atmosphere to trigger tropospheric photochemistry. Here, the absorption spectrum and the 0( D) production quantum yields in the photolysis in the troposphere are described in detail. 

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