Electronic states oxygen atom

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 ... 

Table 4.2 summarizes the threshold wavelengths for production of ground-state.oxygen atoms, 0(3P), as well as electronically excited O( D) and O( S) atoms. Dissociation of 02 in the 175- to 242-nrn region to produce atoms is particularly important in the stratosphere because it is the only significant source of 03 via reactions (1) and (2) (see Chapter 12) ... 

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

The onset of the continuum of the Schumann-Runge absorption bands of 02 is at 1750.5 A. The lower electronic state of the transition is the ground state and dissociates to ground-state oxygen atoms the excited... 

The reaction between ground state oxygen atoms 0(3P) and the monoflu-orocarbene species CHF(X1A ) possesses all three features of the PES discussed above. The reaction proceeds at almost gas-kinetic rate at room temperature [128,129], and the reaction channel (12) to produce CO and HF products in their ground electronic states (in a spin-forbidden process) is one of the most exothermic bimolecular reactions known, and several other product channels, such as reactions (13) and (14) as well as the production of electronically excited states, can occur. Pulsed IR chemiluminescence was observed following IRMPD of 10-40 mTorr of CH2F2 in the presence of O atoms (5-25 mTorr, and measured by titration), and was passed through the SS interferometer and recorded by one of three detectors InSb (1840-... 

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). 

The lowest excited state of most ketones has the (n, n ) electronic structure, which gives the carbonyl (C=0) double bond a 1,2-biradical character. Therefore, the electron-deficient oxygen atom of this moiety, obtained upon excitation, acquires a radical reactivity, similar to the alkoxy radical. This excited state property of ketones leads to intramolecular H-abstraction to form 1-hydroxy-l, x-biradicals. Depending upon the structure and reaction conditions of the carbonyl compound, two common competing reactions may follow ... 

Electronically excited NO has been observed as a product of the reaction of ground state oxygen atoms with nitric oxide. In the first [447], the emission results from the two-body radiative recombination reaction... 

It also seems of interest to compare the stabilities of tetrahedral states of aluminum and boron in terms of this simple qualitative picture. The calculations have revealed that the planar structure is preferential for B(OH)3 as well. The value of r for B(OH)3 is 30.1 kcal/mol, that is, it exceeds substantially the value for Al(OH)3. This is a manifestation of the difference in the covalent radii of B and Al. The value of Ec for the B(OH)3 + HzO system is no longer sufficient to compensate Er, that is, in this system the tetrahedral coordination of the boron atom is unfavorable. However, in the B(OH)3 + OH" system, Ec = 88.4 kcal/mol, that is, the presence of the highly electron-donating oxygen atom of OH- should make the tetrahedral state of boron preferential. Actually, the tetrahedral boron is known to exist in a number of mixed oxides. 

The reactions between ground-state oxygen atoms and CO have been the subject of many investigations because of the important role they play in carbon monoxide flames and explosions. Basically, two reactions (or reaction sequences) occur one produces ground-state CO2, the other produces electronically excited CO2 which is responsible for the chemiluminescent radiation that used to be referred to as the carbon monoxide flame bands. 

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)] ... 

A ground-state oxygen atom has four electrons in the p-orbitals. This... 

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